Neurogenic mechanisms in bladder and bowel ageing

The prevalence of both urinary and faecal incontinence, and also chronic constipation, increases with ageing and these conditions have a major impact on the quality of life of the elderly. Management of bladder and bowel dysfunction in the elderly is currently far from ideal and also carries a significant financial burden. Understanding how these changes occur is thus a major priority in biogerontology. The functions of the bladder and terminal bowel are regulated by complex neuronal networks. In particular neurons of the spinal cord and peripheral ganglia play a key role in regulating micturition and defaecation reflexes as well as promoting continence. In this review we discuss the evidence for ageing-induced neuronal dysfunction that might predispose to neurogenic forms of incontinence in the elderly.

Related papers:

title: Fecal incontinence in the elderly patient.
abstract: Fecal incontinence is an underreported problem in the general population; it is especially common in elderly persons (aged >or=65 years) residing in the community or in long-term care settings. It affects more women than men during younger years, but this differential narrows with age. Physiological changes such as sphincter muscle and sensory abnormalities in the anorectal region contribute to this problem, as do factors such as dementia, physical disability, and fecal impaction. Treatment with biofeedback is feasible in many elderly patients. Those with advanced dementia or physical disability may benefit from a bowel habit training program. Selected patients may require surgical sphincter repair. Minimally invasive techniques such as radiofrequency energy application offer promising future treatment options. The purpose of this review is to provide current information on fecal incontinence and its management in the elderly.

title: Lower urinary tract symptoms and urinary incontinence in a geriatric cohort – a population‐based analysis
abstract: Study Type – Symptom prevalence (prospective cohort)

title: Update on the management of constipation in the elderly: new treatment options
abstract: Constipation disproportionately affects older adults, with a prevalences of 50% in community-dwelling elderly and 74% in nursing-home residents. Loss of mobility, medications, underlying diseases, impaired anorectal sensation, and ignoring calls to defecate are as important as dyssynergic defecation or irritable bowel syndrome in causing constipation. Detailed medical history on medications and co-morbid problems, and meticulous digital rectal examination may help identify causes of constipation. Likewise, blood tests and colonoscopy may identify organic causes such as colon cancer. Physiological tests such as colonic transit study with radio-opaque markers or wireless motility capsule, anorectal manometry, and balloon expulsion tests can identify disorders of colonic and anorectal function. However, in the elderly, there is usually more than one mechanism, requiring an individualized but multifactorial treatment approach. The management of constipation continues to evolve. Although osmotic laxatives such as polyethylene glycol remain mainstay, several new agents that target different mechanisms appear promising such as chloride-channel activator (lubiprostone), guanylate cyclase agonist (linaclotide), 5HT4 agonist (prucalopride), and peripherally acting μ-opioid receptor antagonists (alvimopan and methylnaltrexone) for opioid-induced constipation. Biofeedback therapy is efficacious for treating dyssynergic defecation and fecal impaction with soiling. However, data on efficacy and safety of drugs in elderly are limited and urgently needed.

title: Incontinence in the elderly: prevalence and prognosis.
abstract: In a randomly selected sample of 559 subjects 65 years and over living in the community and in institutions the prevalence of urinary incontinence was found to be 11.6%. In those 80 years and over the prevalence rose to 21.7%. Those with dementia were more likely to be incontinent than those with normal mental function. In the majority of those over 80 who were incontinent, the incontinence was associated with either confusion or a combination of factors. The estimated population prevalence of faecal incontinence for those 65 years and over was 3.1%. Urinary incontinence was associated with an increased risk of death. In a review of subjects after three years 73.5% of the incontinent group had died while only 34.9% of those originally continent had died. Because incontinent elderly people are commonly frail, with a number of conditions contributing to the disorder, the extent of investigation of the disorder needs to be carefully assessed for each patient.

title: Urinary and faecal incontinence in community-residing elderly women.
abstract: The prevalence of urinary and faecal incontinence was investigated in a sample of 1049 women aged 60 years and over in the municipality of Amstelveen, the Netherlands; 719 postal histories were completed. The overall prevalence of urinary incontinence was 23.5%. Daily urine loss was reported by 14.0% of all women. In women aged 60 to 84 years and 85 years and over 4.2% and 16.9% were faecally incontinent, respectively. In all age groups poor mobility and frequency were associated with urinary incontinence. Urgency was independently associated in women aged 60-85 years as was nocturia in women aged 85 years and over.

title: Prevalence of urinary, fecal and double incontinence in the elderly living at home
abstract: The aim of this study was to evaluate the prevalence of urinary, fecal and double incontinence in the elderly, through a population-based cross-sectional survey. The study included all patients aged 60 and over of nine general practices in the Nijmegen Monitoring Project. Patients living in a home for the elderly were excluded, as well as patients with dementia, patients who were too ill to participate and patients with a catheter. There were 5278 selected patients who received a postal questionnaire. Of these, 88% returned it. Nineteen percent of the respondents had involuntary loss of urine twice a month or more, 6% loss of feces and 3% both. The prevalence of urinary, fecal and double incontinence increased with age in both men and women, and especially in men in the oldest age group. Urinary incontinence was more prevalent in women than in men. The prevalence of fecal incontinence showed no sex differences, but the type of fecal incontinence did differ between men and women. In men loss of mucus was twice as common as in women. Double incontinence was also equally prevalent in men and women, except in the age group 65-74 years. In conclusion, urinary, fecal and double incontinence are common conditions in the community-dwelling population. The prevalence rates increase with age. Urinary incontinence is more prevalent in women. There were no sex differences in the prevalence of fecal incontinence but the type of fecal incontinence was different in men and women.

title: Population-based survey of urinary incontinence, overactive bladder, and other lower urinary tract symptoms in five countries: results of the EPIC study.
abstract: Estimate the prevalence of urinary incontinence (UI), overactive bladder (OAB), and other lower urinary tract symptoms (LUTS) among men and women in five countries using the 2002 International Continence Society (ICS) definitions.



This population-based, cross-sectional survey was conducted between April and December 2005 in Canada, Germany, Italy, Sweden, and the United Kingdom using computer-assisted telephone interviews. A random sample of men and women aged >/= 18 yr residing in the five countries and who were representative of the general populations in these countries was selected. Using 2002 ICS definitions, the prevalence estimates of storage, voiding, and postmicturition LUTS were calculated. Data were stratified by country, age cohort, and gender.



A total of 19,165 individuals agreed to participate; 64.3% reported at least one LUTS. Nocturia was the most prevalent LUTS (men, 48.6%; women, 54.5%). The prevalence of storage LUTS (men, 51.3%; women, 59.2%) was greater than that for voiding (men, 25.7%; women, 19.5%) and postmicturition (men, 16.9%; women, 14.2%) symptoms combined. The overall prevalence of OAB was 11.8%; rates were similar in men and women and increased with age. OAB was more prevalent than all types of UI combined (9.4%).



The EPIC study is the largest population-based survey to assess prevalence rates of OAB, UI, and other LUTS in five countries. To date, this is the first study to evaluate these symptoms simultaneously using the 2002 ICS definitions. The results indicate that these symptoms are highly prevalent in the countries surveyed.

title: The extent and severity of urinary incontinence amongst women in UK GP waiting rooms.
abstract: Few women seek help for urinary incontinence. Subsequently, there may be many women accessing primary care services who would benefit from treatment or advice. If high levels of unexpressed need are present in this population, a more proactive approach to continence management may be appropriate, but the feasibility of this depends on an accurate assessment of the level of unmet need in this population.



To assess the prevalence of urinary incontinence in a female population attending primary care and the extent of treatment seeking in relation to level of need.



A cross-sectional survey of urinary incontinence of adult women attending primary care practices in West Yorkshire, London, Glasgow and Leicestershire during a 10- or 15-day period.



Three thousand two hundred and seventy-three (54%) women responded. Twenty-one per cent reported stress urinary incontinence only, 3.5% reported urge incontinence only and 21% reported mixed stress and urge incontinence during the preceding month (9% had moderate or severe symptoms). Fifty-three per cent of these had not consulted a health care professional, which is equivalent to 1 in 20 of women in GP waiting rooms, most of whom have stress and urge incontinence (75%) or stress incontinence only (21%).



Nearly half of female primary care attendees had experienced incontinence during the preceding month, but only a minority had sought help. Even amongst the nearly 1 in 10 women with moderate or severe incontinence only about half had sought help. There remains considerable health decrement due to urinary incontinence in those not receiving help in a population readily accessible to primary care services.

title: Effect of Urinary Incontinence on Older Nursing Home Residents’ Self‐Reported Quality of Life
abstract: To evaluate the effect of urinary incontinence (UI) on elderly nursing home (NH) residents’ self‐reported quality of life (QOL), especially on the specific QOL domains most closely associated with UI.

title: Fecal incontinence in the institutionalized elderly: incidence, risk factors, and prognosis.
abstract: This study was conducted to evaluate the incidence, identify the risk factors, and assess the prognosis of elderly institutionalized patients who develop fecal incontinence.



We enrolled 1,186 patients 60 years of age and older living in long-term care facilities who did not have fecal incontinence. We assessed their medical history, treatment, mobility, and cognitive function. Patients were followed up for 10 months to determine the incidence of fecal incontinence, defined as at least one involuntary loss of feces. Independent risk factors associated with fecal incontinence were identified using Cox proportional hazards models. The prognosis of incontinent patients was assessed by comparing their survival rate with that in the continent patients.



Fecal incontinence occurred in 234 patients (20%), and was usually associated with acute diarrhea or fecal impaction. We identified five risk factors for the development of fecal incontinence: a history of urinary incontinence (rate ratio [RR]: 2.0, 95% confidence interval [CI] 1.5 to 2.6); neurological disease (RR: 1.9, 95% CI 1.0 to 3.4); poor mobility (RR: 1.7, 95% CI 1.2 to 2.4); severe cognitive decline (RR: 1.4, 95% CI 1.1 to 1.9); and age older than 70 years (RR: 1.7, 95% CI 1.0 to 2.8). Ten-month mortality in the 89 patients with long-term (> or = 8 days) incontinence was 26%, significantly greater than that observed in the continent group (6.7%) or in the 145 patients with transient incontinence (10%).



Long-lasting or permanent fecal incontinence was associated with increased mortality, suggesting that this symptom is a marker of poor health in older patients. Actions that improve mobility might help prevent fecal incontinence in elderly patients.

title: Faecal incontinence in residential homes for the elderly: prevalence, aetiology and management.
abstract: Faecal incontinence occurring at least once weekly was found in 10.3% of residents in 30 residential homes for the elderly. Fifty-two randomly-selected incontinent residents were prescribed treatment and the outcome was compared with 30 incontinent residents acting as controls. The vast majority of all incontinent residents showed evidence of chronic brain failure (dementia). Incontinence had been present for over a year in 73%, yet only 4% had been referred to their general practitioner. Incontinence secondary to constipation or impaction and neurogenic incontinence were equally common. Full compliance with the recommended treatment was obtained in 66%, and 87% of these were cured. This compared with 32% of the control group during the same period (P less than 0.001). This study confirms that in the great majority of cases faecal incontinence in old people is both curable and preventable.

title: Fecal impaction: a cause for concern?
abstract: Fecal impaction (FI) is a common cause of lower gastrointestinal tract obstruction lagging behind stricture for diverticulitis and colon cancer. It is the result of chronic or severe constipation and most commonly found in the elderly population. Early recognition and diagnosis is accomplished by way of an adequate history and physical examination in conjunction with an acute abdominal series. Prompt identification and treatment minimizes the risks of complications such as bowel obstruction leading to aspiration, stercoral ulcers, perforation, and peritonitis. Treatment options include gentle proximal softening in the absence of complete bowel obstruction, distal washout, and manual extraction. Surgical resection of the involved colon or rectum is reserved for cases of FI complicated by ulceration and perforation leading to peritonitis. Recurrence is common, and can be managed by increasing dietary fiber content to 30 gm/day, increased water intake, and discontinuation of medications that can contribute to colonic hypomotility.

title: Obstetric Factors Associated With Levator Ani Muscle Injury After Vaginal Birth
abstract: To identify obstetric factors associated with development of levator ani injury after vaginal birth.  Magnetic resonance images were taken of the pelvic floor of 160 women 9 to 12 months after first term vaginal delivery. Half the women had de novo stress incontinence and half were continent controls. Abnormalities of the pubovisceral portion were identified on magnetic resonance as present or absent. Defect severity was further scored in each muscle from 0 (no defect) to 3 (complete muscle loss). A summed score for the 2 sides (0 to 6) was assigned and grouped as minor (0–3) or major (4–6). Obstetric details were collected. The association between obstetric variables and muscle injury were analyzed using Fisher exact test and t tests.  The following increased odds ratios for levator defect were found: forceps use 14.7 (95% confidence interval [CI] 4.9–44.3), anal sphincter rupture 8.1 (95% CI 3.3–19.5) and episiotomy 3.1 (95% CI 1.4–7.2) but not vacuum delivery 0.9 (95% CI 0.19–4.3), epidural use 0.9 (95% CI 0.4–2.0), or oxytocin use 0.8 (95% CI 0.3–1.8). Women with levator injury were 3.5 years older and had a 78-minute longer second stage of labor. Differences in gestational age, birth weight, and head circumference were not statistically significant. A major defect in the pubovisceral muscle was seen in 22 women and a minor defect in 7 women.  Injuries to the levator ani muscles in women after their first vaginal delivery are associated with several obstetric factors indicating difficult vaginal birth and with older age.

title: Obstetric anal sphincter injury in the UK and its effect on bowel, bladder and sexual function.
abstract: To determine the incidence and factors associated with the development of bowel, urinary and sexual symptoms following obstetric anal sphincter injury (OASIS).



A prospective cohort study involving 435 women who sustained OASIS, over a five-year period, in a large UK teaching hospital. Details of bowel, urinary and sexual function were documented using a structured questionnaire. The outcome measures included the incidence of symptoms following OASIS and factors which modify the risk of developing symptoms.



The majority (96%) of women were faecally continent three months after primary OASIS repair. Nevertheless, 34.2% reported faecal urgency, 25% suffered poor flatal control, and nearly 30% reported pain and bleeding on defaecation. Sixteen percent of women reported stress urinary incontinence, 15% experienced urgency and 20% reported urinary frequency. Fifty-seven percent of women had resumed intercourse but 32% of those women reported dyspareunia. Women who developed faecal symptoms were significantly more likely to develop urinary symptoms. Advancing maternal age and the use of forceps, in particular rotational forceps, significantly increase the risk of developing faecal and urinary symptoms.



Obstetric anal sphincter injuries continue to be responsible for significant morbidity, with approximately 30% of women reporting faecal, urinary or sexual symptoms, three months postpartum. This large prospective UK study provides up-to-date information relating to factors which increase the likelihood of such symptoms occurring. These data are useful for counselling and targeting more intensive follow up to women at higher risk of developing symptoms.

title: The female pelvic floor through midlife and aging.
abstract: Female pelvic floor is a complex functional unit involved in multiple functions that extend beyond the sole support of pelvic organs. Pelvic floor dysfunction globally affects micturition, defecation and sexual activity. Evolutionary modifications such ad adaptation to upright standing, walking and the need to deliver fetuses with larger head diameters made the fascial and muscle support of the pelvic floor vulnerable, therefore predisposing women to pelvic organ prolapse and incontinence. Different than in males, the female pelvic floor undergoes a number of adaptive changes related to life and endocrine events. Most of the clinical manifestations of these changes become apparent after menopause and throughout aging in women. This review article summarizes the key aspects of the pathophysiology and the clinics of the modifications of the pelvic floor in women through midlife and beyond. A particular focus is given to the relationship between urinary and bowel dysfunction.

title: Epidemiology of constipation (EPOC) study in the United States: relation of clinical subtypes to sociodemographic features
abstract: Constipation is a common heterogeneous condition, possibly encompassing different clinical subtypes. Little is known about the comparative epidemiology of constipation subtypes. This study was conducted to estimate the prevalence of constipation subtypes and determine whether subtypes differ by sociodemographic factors.Between June and September 1997, a telephone interview was conducted with individuals about their bowel habits in the preceding 3 months. Survey data on 15 constipation-related symptoms were used to identify individuals who met prespecified symptom criteria for the following mutually exclusive subgroups: functional constipation, irritable bowel syndrome (IBS), outlet obstruction or delay (outlet), both IBS and outlet (IBS-outlet), and frequent laxative users (i.e., at least every other day). A total of 10,018 eligible individuals in the United States 18 yr of age or older completed the interview. Test–retest reliability of reporting symptoms was assessed in a separate national survey. The Spearman's correlation coefficient for reporting symptoms ranged from 0.54 to 0.83; all but three symptoms had correlations above 0.68.RESULTS:The overall prevalence of constipation was 14.7%. By subtype, prevalence was 4.6% for functional, 2.1% for IBS, 4.6% for outlet, and 3.4% for IBS-outlet. An additional 1.8% of respondents reported laxative use at least every other day. Outlet was the most common subtype among women, whereas functional constipation was the most common subtype among men. The gender ratio varied by subtype, with elevated ratios for outlet (F/M = 1.65) and IBS-outlet (F/M = 2.27) subtypes. The age pattern differed among each of the four subtypes. Prevalence of functional subtype decreased with increasing age. In contrast, outlet subtype did not seem to vary by age, and IBS (both men and women) and IBS-outlet (women only) subtypes increased to age 35 yr and declined thereafter. Prevalence of functional constipation increased with increasing education. Outlet type was more common in nonwhites compared to whites. Finally, 45% of individuals with constipation reported having the condition for 5 yr or more.Constipation is a heterogeneous condition. Differences in epidemiological profile by age, sex ratio, and relation to other sociodemographical factors support the distinction of two and possibly more symptom-based subtypes.

title: Constipation in an elderly community: a study of prevalence and potential risk factors.
abstract: The epidemiology of chronic constipation in the elderly remains poorly defined. We aimed to study the prevalence of, and potential risk factors for, constipation in a representative elderly community, using symptom-based diagnostic criteria.



An age and gender-stratified random sample of 1833 eligible residents of Olmsted County, Minnesota, aged 65 yr and over, was mailed a valid self-report questionnaire; 1375 responded (75%).



The overall age- and gender-adjusted prevalence (per 100) of any constipation was 40.1 (95% CI 38.9, 44.4); for functional constipation and outlet difficulty or delay, the prevalence rates were 24.4 (95% CI 22.0-26.9) and 20.5 (95% CI 18.2-22.8), respectively. Self-reported constipation did not reliably identify functional constipation or outlet delay. Outlet delay, but not functional constipation, was more frequent in women; functional constipation, but not outlet delay, was associated with advancing age. Nonsteroidal anti-inflammatory drugs and other medications were significant risk factors in subjects with functional constipation and outlet delay combined.



In independently living, elderly persons, constipation is a common complaint; among these subjects, there appear to be symptom subgroups that can be identified.

title: Physiology of the ageing gut
abstract: will review the recent publications (over the last 1–2 years) concerning the effects of ageing on gastrointestinal function, with an emphasis on the motor and sensory function of the gut. Recent findingsRecent publications support earlier observations of an age-related selective decline in the number of cholinergic neurons in the enteric nervous system, but also reveal a progressive loss of interstitial cells of Cajal in the stomach and colon throughout adult life. These changes appear to have surprisingly little effect on gastrointestinal motor function in healthy ageing, although gut sensation is impaired and older individuals have an increased susceptibility to gastrointestinal complications of comorbid illnesses. SummaryAlterations in gut function with ageing have particular implications in the oesophagus, colon, and anorectum. Dysphagia, gastro-oesophageal reflux disease, constipation, and faecal incontinence are the most prevalent clinical manifestations. Older individuals are also susceptible to postprandial hypotension, in which altered cardiovascular responses to intestinal nutrient exposure are pivotal. Dysphagia, delayed gastric emptying, and constipation are increasingly being recognized as early features of Parkinson's disease, and frequently precede the neurological manifestations.

title: Management of faecal incontinence and constipation in adults with central neurological diseases.
abstract: People with central neurological disease or injury have a much higher risk of both faecal incontinence and constipation than the general population. There is often a fine line between the two symptoms, with any management intended to ameliorate one risking precipitating the other. Bowel problems are observed to be the cause of much anxiety and may reduce quality of life in these people. Current bowel management is largely empirical, with a limited research base. This is an update of a Cochrane review first published in 2001 and subsequently updated in 2003 and 2006. The review is relevant to individuals with any disease directly and chronically affecting the central nervous system (post-traumatic, degenerative, ischaemic or neoplastic), such as multiple sclerosis, spinal cord injury, cerebrovascular disease, Parkinson's disease and Alzheimer's disease.



To determine the effects of management strategies for faecal incontinence and constipation in people with a neurological disease or injury affecting the central nervous system.



We searched the Cochrane Incontinence Group Trials Register (searched 8 June 2012), which includes searches of the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE and MEDLINE In-Process as well as handsearching of journals and conference proceedings; and all reference lists of relevant articles.



Randomised and quasi-randomised trials evaluating any type of conservative or surgical intervention for the management of faecal incontinence and constipation in people with central neurological disease or injury were selected. Specific therapies for the treatment of neurological diseases that indirectly affect bowel dysfunction were also considered.



At least two review authors independently assessed the risk of bias of eligible trials and independently extracted data from the included trials using a range of pre-specified outcome measures.



Twenty trials involving 902 people were included. Oral medications There was evidence from individual small trials that people with Parkinson's disease had a statistically significant improvement in the number of bowel motions or successful bowel care routines per week when fibre (psyllium) (mean difference (MD) -2.2 bowel motions, 95% confidence interval (CI) -3.3 to -1.4) or oral laxative (isosmotic macrogol electrolyte solution) (MD 2.9 bowel motions per week, 95% CI 1.48 to 4.32) are used compared with placebo. One trial in people with spinal cord injury showed statistically significant improvement in total bowel care time comparing intramuscular neostigmine-glycopyrrolate (anticholinesterase plus an anticholinergic drug) with placebo (MD 23.3 minutes, 95% CI 4.68 to 41.92).Five studies reported the use of cisapride and tegaserod in people with spinal cord injuries or Parkinson's disease. These drugs have since been withdrawn from the market due to adverse effects; as they are no longer available they have been removed from this review. Rectal stimulants One small trial in people with spinal cord injuries compared two bisacodyl suppositories, one polyethylene glycol-based (PGB) and one hydrogenated vegetable oil-based (HVB). The trial found that the PGB bisacodyl suppository significantly reduced the mean defaecation period (PGB 20 minutes versus HVB 36 minutes, P < 0.03) and mean total time for bowel care (PGB 43 minutes versus HVB 74.5 minutes, P < 0.01) compared with the HVB bisacodyl suppository. There was evidence from one small trial with 31 participants that abdominal massage statistically improved the number of bowel motions in people who had a stroke compared with no massage (MD 1.7 bowel motions per week, 95% CI 2.22 to 1.18). A small feasibility trial including 30 individuals with multiple sclerosis also found evidence to support the use of abdominal massage. Constipation scores were statistically better with the abdominal massage during treatment although this was not supported by a change in outcome measures (for example the neurogenic bowel dysfunction score).One small trial in people with spinal cord injury showed statistically significant improvement in total bowel care time using electrical stimulation of abdominal muscles compared with no electrical stimulation (MD 29.3 minutes, 95% CI 7.35 to 51.25).There was evidence from one trial with a low risk of bias that for people with spinal cord injury transanal irrigation, compared against conservative bowel care, statistically improved constipation scores, neurogenic bowel dysfunction score, faecal incontinence score and total time for bowel care (MD 27.4 minutes, 95% CI 7.96 to 46.84). Patients were also more satisfied with this method.Other interventions In one trial in stroke patients, there appeared to be a short term benefit (less than six months) to patients in terms of the number of bowel motions per week with a one-off educational intervention from nurses (a structured nurse assessment leading to targeted education versus routine care), but this did not persist at 12 months. A trial in individuals with spinal cord injury found that a stepwise protocol did not reduce the need for oral laxatives and manual evacuation of stool.Finally, one further trial reported in abstract form showed that oral carbonated water (rather than tap water) improved constipation scores in people who had had a stroke.



There is still remarkably little research on this common and, to patients, very significant issue of bowel management. The available evidence is almost uniformly of low methodological quality. The clinical significance of some of the research findings presented here is difficult to interpret, not least because each intervention has only been addressed in individual trials, against control rather than compared against each other, and the interventions are very different from each other.There was very limited evidence from individual trials in favour of a bulk-forming laxative (psyllium), an isosmotic macrogol laxative, abdominal massage, electrical stimulation and an anticholinesterase-anticholinergic drug combination (neostigmine-glycopyrrolate) compared to no treatment or controls. There was also evidence in favour of transanal irrigation (compared to conservative management), oral carbonated (rather than tap) water and abdominal massage with lifestyle advice (compared to lifestyle advice alone). However, these findings need to be confirmed by larger well-designed controlled trials which should include evaluation of the acceptability of the intervention to patients and the effect on their quality of life.

title: Anorectal function in elderly patients with fecal impaction.
abstract: Manometric and other investigations were carried out in 55 elderly patients who had impacted masses of feces in the rectum upon admission to hospital and in 36 elderly age- and sex-matched control subjects. Maximum basal and maximum squeeze sphincter pressures in the patients were similar to those in the elderly controls. Most elderly patients in the impacted group and all control subjects were able to pass a 50-ml balloon from the rectum, although a lower proportion of patients, admitted with impaction, could expel a small solid sphere. In patients the rectum had to be distended with larger volumes than in controls before the presence of the rectal balloon, pain, and the desire to defecate were perceived and before rectal contractions were generated. Rectal pressures, recorded during rectal distention, were lower in the impacted group than in the control group. Finally, anal and perianal sensation was impaired in patients with fecal impaction. These findings are similar to those described in patients with low spinal cord injuries.

title: Fecal impaction.
abstract: Fecal impaction is a common gastrointestinal problem and a potential source of major morbidity. Prompt identification and treatment minimize the risks of complications. Treatment options include manual extraction and proximal or distal washout. Following treatment, possible etiologies should be sought and preventive therapy instituted.

title: The burden of constipation on quality of life: results of a multinational survey
abstract: The impact of constipation on quality of life (QoL) may vary in different cultural or national settings.

title: Psychosocial and societal burden of incontinence in the aged population: a review
abstract: As the adults age, the risk of both urinary and fecal incontinence increases, the result of natural degenerative changes in concert with concomitant issues of aging such as infection, polypharmacy, and decreased cognitive function. Most adults past the age of 65 suffer incontinence on some level, with significant and often devastating impact on the physical and emotional health of the patient. Incontinence in the older adult is a humiliating and disabling disorder, which causes substantial stress, depression, and limitation. It can impede interpersonal relationships, decrease sexual function, and increase the risk of debilitating falls, institutionalization, and even increase mortality. Incontinence also represents a substantial economic burden to the general population. Nonetheless, incontinence is often undiagnosed, and when diagnosed, often left untreated. Although common in older adults, incontinence is not an inevitable consequence of aging but a disorder that can and should be treated. Appropriate clinical management of incontinence can help seniors continue to lead vital, active lives as well as avoid the cutaneous sequelae of this disorder.

title: The association between urinary and fecal incontinence and social isolation in older women.
abstract: To describe the association between social isolation and urinary incontinence and fecal incontinence in older women.



We conducted a secondary database analysis of the National Social Life, Health and Aging Project for women aged 57 to 85 years old. Our primary outcome was self-report of often feeling isolated. We explored self-report of daily urinary incontinence and weekly fecal incontinence. Two logistic regression analyses were performed to assess the association between often feeling isolated and (1) daily urinary incontinence and (2) weekly fecal incontinence.



A total of 1412 women were included in our analysis. Daily urinary incontinence was reported by 12.5% (177/1412) of community-dwelling older women. More women with daily urinary incontinence reported often feeling isolated (6.6%; 95% confidence interval [CI], 1.3-11.9 vs 2.6%; 95% CI, 1.7-3.5; P = .04) compared with women without daily urinary incontinence. Women with daily urinary incontinence had 3.0 (95% CI, 1.1-7.6) increased odds of often feeling isolated after adjusting for depressive symptoms, age, race, education, and overall health. Weekly fecal incontinence was reported by 2.9% (41/1412) of women. Weekly fecal incontinence and often feeling isolated were associated on univariable analysis (crude odds ratio, 4.6; 95% CI, 1.4-15.1). However, after adjusting for depressive symptoms, age, race, education, and overall health the association between weekly fecal incontinence and often feeling isolated was not significant (adjusted odds ratio, 0.65; 95% CI, 0.1-5.3; P = .65).



After adjusting for confounders, daily urinary incontinence was significantly associated with often feeling isolated. Weekly fecal incontinence was not found to be associated with often feeling isolated on multivariable logistic regression.

title: Urinary incontinence and its relationship to mental health and health-related quality of life in men and women in Sweden, the United Kingdom, and the United States.
abstract: Differences in health burden associated with urinary incontinence (UI) subtypes have been previously described, but the majority of studies are in women. Additional research is needed to examine the prevalence and burden of UI subtype including postmicturition incontinence, nocturnal enuresis, coital incontinence, and incontinence for unspecified reasons.



Examine the burden of UI in men and women in Sweden, the United Kingdom, and the United States.



Secondary analyses of the Epidemiology of Lower Urinary Tract Symptoms (EpiLUTS), a cross-sectional Internet survey, were performed. Participants who reported UI were categorized as (1) urgency urinary incontinence (UUI) only, (2) stress urinary incontinence (SUI) only, (3) mixed urinary incontinence (MUI), (4) UUI plus other incontinence (OI), (5) SUI plus OI, or (6) OI. Differences in health outcomes across UI groups were explored by gender using descriptive statistics and general linear models.



Outcomes included treatment seeking for urinary symptoms, perception of bladder condition, depression, anxiety, and health-related quality of life (HRQL).



Of 14 140 men and 15 860 women, 6479 men (45.8%) and 10 717 women (67.6%) reported UI. The most prevalent UI subgroups were OI in men and SUI in women. MUI and SUI plus OI had the greatest treatment seeking among men, whereas MUI and UUI plus OI had the greatest treatment seeking among women. Men with MUI had the highest rates of anxiety, followed by those with UUI plus OI and SUI plus OI, and OI with a similar trend observed for depression. Anxiety and depression were highest in SUI plus OI and MUI women. MUI and UUI plus OI men and women had significantly lower HRQL compared with other UI groups.



UI is common in men and women aged >40. Individuals with UUI combined with SUI or OI bear a greater mental health burden and report poorer HRQL.

title: Under the tip of the iceberg: Psychological factors in incontinence
abstract: To highlight two main psychological factors (cognitive barriers and safety‐behaviors) involved in the development and maintenance of emotional distress in patients with urinary incontinence (UI) and thus facilitate a better understanding of this condition and contribute to a more comprehensive treatment.

title: Validity and reliability of the patient’s perception of intensity of urgency scale in overactive bladder
abstract: Study Type – Prognosis (outcomes research)  Level of Evidence 2c

title: Faecal incontinence: causes, assessment and management.
abstract: Faecal incontinence can be a debilitating, distressing and isolatin condition that affects individuals' quality of life. This article discusses the definition, prevalence and causes of faecal incontinence, emphasises the importance of assessment and examines how this stigmatising condition affects adults. Once a differential diagnosis is made, an appropriate patient-centred treatment plan can be established to improve the individual's symptoms.

title: Qualifying a quantitative approach to women’s expectations of continence surgery
abstract: Introduction and hypothesisThe objective of this study is to explore expectations and goals of women undergoing continence surgery using a combined quantitative and qualitative approach.MethodsWomen with urinary incontinence, recruited from the waiting list, were assessed with a structured clinical interview, and these data were transcribed and analysed thematically (grounded theory). The Kings Health Questionnaire (KHQ) was used to determine incontinence impact on patient’s life.ResultsIncontinence was objectively quantified using videocystourethrography. KHQ quantitative analysis suggested that the main domains affected were incontinence impact on life and physical limitations. However, qualitative analysis based on the interview found women were most affected by incontinence impact on physical or social limitation, sexual function, emotions and body image.ConclusionWhilst disease-specific QoL questionnaires allow broad comparisons to be made assessing patient bother; they lack sensitivity to assess individual symptoms. A qualitative approach may individualise patient care and improve patient satisfaction and overall outcome.

title: Mortality in relation to urinary and faecal incontinence in elderly people living at home.
abstract: To examine the relationship between incontinence and mortality in elderly people living at home.



Of the randomly selected people aged 65 years and older living in Settsu city, Osaka in October 1992, 1405 were contacted and constituted the study cohort. Follow-up for 42 months was completed for 1318 (93.8%; 1129 alive, 189 dead).



Data on general health status, history of health management, psychosocial conditions and urinary and faecal incontinence were collected by interview during home visits at the time of enrolment.



From the Kaplan-Meier analysis, the estimated survival rates decreased with a decline in continence in both the 65-74 and 75 years and older age groups. From the Cox proportional hazards model, unadjusted hazard ratios of minor, moderate and severe incontinence for mortality, compared with continence, were 2.27, 2.96 and 5.94, respectively. Multivariate analysis yielded adjusted hazard ratios of minor, moderate and severe incontinence of 0.99, 1.17 and 1.91, respectively, leaving severe incontinence as the significant factor, when other indicators are controlled.



Incontinence is related to mortality and severe incontinence represents an increased risk factor for mortality in elderly people living at home.

title: Impact of Persistent Constipation on Health-Related Quality of Life and Mortality in Older Community-Dwelling Women
abstract: Very little is known about whether the reported health-related impact of constipation is worse in people who experience constipation over a long period of time vs. those with more transient symptoms. We aimed to determine the impact of persistent vs. transient constipation on health-related quality of life (QOL), depression, and mortality.We analyzed data from 5,107 women (aged 70–75 years in 1996) who answered “Have you had constipation in the past 12 months?” in all five surveys sent out every 3 years of the Australian Longitudinal Study on Women’s Health.Of the 5,107 women, 20.9, 54.1, and 24.7% reported having persistent constipation on at least 4 out of 5 surveys, transient constipation reported on 1–3 surveys, or none reported over the 15-year time frame, respectively. Women who reported persistent constipation had significantly lower scores for all domains of QOL on the SF-36 except role-emotional, and had higher levels of self-reported depression, even after adjusting for number of chronic illnesses and fluid intake. Mortality rates were increased when comparing women with no reported constipation with persistently reported constipation (8.2% vs. 11%, odds ratio = 1.32, 95% confidence interval 1.0, 1.74, P = 0.05) controlling for specific chronic illnesses.Persistent constipation among older women is associated with poor health outcomes.

title: The economic impact of overactive bladder syndrome in six Western countries
abstract: To calculate up‐to‐date estimates of the economic impact of overactive bladder syndrome (OAB) with and without urgency urinary incontinence (UUI) on the health sector of six countries (Canada, Germany, Italy, Spain, Sweden and the UK), as OAB is a significant health concern for adults aged >18 years living in Western countries.

title: Economic Cost of Fecal Incontinence
abstract: Despite its prevalence and deleterious impact on patients and families, fecal incontinence remains an understudied condition. Few data are available on its economic burden in the United States.  The aim of this study was to quantify per patient annual economic costs associated with fecal incontinence.  A mail survey of patients with fecal incontinence was conducted in 2010 to collect information on their sociodemographic characteristics, fecal incontinence symptoms, and utilization of medical and nonmedical resources for fecal incontinence. The analysis was conducted from a societal perspective and included both direct and indirect (ie, productivity loss) costs. Unit costs were determined based on standard Medicare reimbursement rates, national average wholesale prices of medications, and estimates from other relevant sources. All cost estimates were reported in 2010 US dollars.  This study was conducted at a single tertiary care institution.  The analysis included 332 adult patients who had fecal incontinence for more than a year with at least monthly leakage of solid, liquid, or mucous stool.  The primary outcome measured was the per patient annual economic costs associated with fecal incontinence.  The average annual total cost for fecal incontinence was $4110 per person (median = $1594; interquartile range, $517–$5164). Of these costs, direct medical and nonmedical costs averaged $2353 (median, $1176; interquartile range, $294–$2438) and $209 (median, $75; interquartile range, $17–$262), whereas the indirect cost associated with productivity loss averaged $1549 per patient annually (median, $0; interquartile range, $0–$813). Multivariate regression analyses suggested that greater fecal incontinence symptom severity was significantly associated with higher annual direct costs.  This study was based on patient self-reported data, and the sample was derived from a single institution.  Fecal incontinence is associated with substantial economic cost, calling for more attention to the prevention and effective management of this condition.

title: The cost‐effectiveness of macrogol 3350 compared to lactulose in the treatment of adults suffering from chronic constipation in the UK
abstract: It is unknown whether macrogol 3350 (Movicol) affords the UK’s National Health Service (NHS) a cost‐effective addition to the current range of laxatives.

title: A healthy bladder: a consensus statement
abstract: A panel of experts in urology, urogynecology, nursing, and behavioral therapy convened in 2010 to discuss the importance of a healthy bladder on overall health. They determined that a consensus statement was necessary to raise awareness among the general public, healthcare providers, payors, and policymakers, with the goals of minimizing the impact of poor bladder health and stimulating primary prevention of bladder conditions. In this statement, ‘healthy’ bladder function is described, as well as internal and external factors that influence bladder health. It is suggested that primary prevention strategies should be aimed at providing education regarding normal lower urinary tract structures and functioning to the public, including patients and healthcare providers. This education may promote the achievement of optimal bladder health by increasing healthy bladder habits and behaviors, awareness of risk factors, healthcare seeking, and clinician engagement and reducing stigma and other barriers to treatment. Promoting optimal bladder health may reduce the personal, societal and economic impact of bladder conditions, including anxiety and depression and costs associated with conditions or diseases and their treatment. While adopting healthy bladder habits and behaviors and behaviors may improve or maintain bladder health, it is important to recognize that certain symptoms may indicate the presence of conditions that require medical attention; many bladder conditions are treatable with a range of options for most bladder conditions. Lastly, the authors propose clinical directives based on persuasive and convergent research to improve and maintain bladder health. The authors hope that this statement will lead to promotion and achievement of optimal bladder health, which may improve overall health and help minimize the effects of bladder conditions on the public, healthcare professionals, educators, employers, and payors. The advisors are in consensus regarding the recommendations for improving and maintaining bladder health presented herein.

title: The integrative physiology of the bladder.
abstract: Normal bladder function is complex, resulting from the co-operative interaction of numerous regulatory cell types, of which the interstitial cells and the peripheral neurones are particularly interesting. Collectively, these comprise the myovesical plexus, which appears to confer structural and functional characteristics on the bladder loosely akin to those of the gut. These include functional modularity, which gives rise to the potential for localised and propagating peristalsis-like movements in the bladder wall according to the prevailing physiological conditions. Localised modular activity during filling may contribute to normal generation of sensation and exaggerated modular activity may give rise to urinary urgency. Enhanced co-ordination of modular activity occurs in various models of detrusor overactivity; it leads to surges of contraction over a large part of the bladder wall, generating phasic changes in intravesical pressure. During voiding, the myovesical plexus sustains detrusor contraction at the behest of the brainstem, monitoring state of bladder fullness as it does so, as a guide to the required duration for which it has to keep up the effort. Accordingly, the bladder wall itself may house structures which render the bladder the effector level in a hierarchy of lower urinary tract regulation. Dysfunction in these vital regulatory structures is an underestimated factor in the pathophysiology of clinical bladder problems.

title: Ganglia within the gut, heart, urinary bladder, and airways: studies in tissue culture.
abstract: Publisher Summary This chapter describes ganglia within the mammalian gut, heart, urinary bladder, and airways. Autonomic ganglia are present in almost all organs of the body and exhibit considerable differences in their structures and properties. The most well-studied intrinsic autonomic ganglia, both in culture and in situ, are those of the enteric nervous system (ENS). The ganglia of the ENS are grouped into two major plexuses: (1) the myenteric (or Auerbach's), which lies between the outer longitudinal and circular smooth-muscle layers and (2) the submucous (or Meissner's), which lies in the connective tissue of the submucosa. The two plexuses are connected by nerves that pass through the circular muscle layer. The enteric neurons are a highly diverse population functionally, morphologically, and with respect to their neurotransmitter phenotypes. The unique advantages of culture preparations, including the increased accessibility of the cultured cells, the ability to observe cells over extended periods of time, and the ability to control their physical and chemical environment, are pertinent in the study of the regulation of phenotypic differentiation.

title: Interstitial cells in the urinary bladder—localization and function
abstract: This review summarizes the currently available literature on the localization and proposed functions of a novel group of cells in the urinary bladder known as interstitial cells or interstitial cells of Cajal (ICC).

title: Bladder interstitial cells: an updated review of current knowledge
abstract: The field of bladder research has been energized by the study of novel interstitial cells (IC) over the last decade. Several subgroups of IC are located within the bladder wall and make structural interactions with nerves and smooth muscle, indicating integration with intercellular communication and key physiological functions. Significant progress has been made in the study of bladder ICs' cellular markers, ion channels and receptor expression, electrical and calcium signalling, yet their specific functions in normal bladder filling and emptying remain elusive. There is increasing evidence that the distribution of IC is altered in bladder pathophysiologies suggesting that changes in IC may be linked with the development of bladder dysfunction. This article summarizes the current state of the art of our knowledge of IC in normal bladder and reviews the literature on IC in dysfunctional bladder.

title: Functional Innervation of Guinea-Pig Bladder Interstitial Cells of Cajal Subtypes: Neurogenic Stimulation Evokes In Situ Calcium Transients
abstract: Several populations of interstitial cells of Cajal (ICC) exist in the bladder, associated with intramural nerves. Although ICC respond to exogenous agonists, there is currently no evidence of their functional innervation. The objective was to determine whether bladder ICC are functionally innervated. Guinea-pig bladder tissues, loaded with fluo-4AM were imaged with fluorescent microscopy and challenged with neurogenic electrical field stimulation (EFS). All subtypes of ICC and smooth muscle cells (SMC) displayed spontaneous Ca2+-oscillations. EFS (0.5 Hz, 2 Hz, 10 Hz) evoked tetrodotoxin (1 µM)-sensitive Ca2+-transients in lamina propria ICC (ICC-LP), detrusor ICC and perivascular ICC (PICC) associated with mucosal microvessels. EFS responses in ICC-LP were significantly reduced by atropine or suramin. SMC and vascular SMC (VSM) also responded to EFS. Spontaneous Ca2+-oscillations in individual ICC-LP within networks occurred asynchronously whereas EFS evoked coordinated Ca2+-transients in all ICC-LP within a field of view. Non-correlated Ca2+-oscillations in detrusor ICC and adjacent SMC pre-EFS, contrasted with simultaneous neurogenic Ca2+ transients evoked by EFS. Spontaneous Ca2+-oscillations in PICC were little affected by EFS, whereas large Ca2+-transients were evoked in pre-EFS quiescent PICC. EFS also increased the frequency of VSM Ca2+-oscillations. In conclusion, ICC-LP, detrusor ICC and PICC are functionally innervated. Interestingly, Ca2+-activity within ICC-LP networks and between detrusor ICC and their adjacent SMC were synchronous under neural control. VSM and PICC Ca2+-activity was regulated by bladder nerves. These novel findings demonstrate functional neural control of bladder ICC. Similar studies should now be carried out on neurogenic bladder to elucidate the contribution of impaired nerve-ICC communication to bladder pathophysiology.

title: Is the urothelium intelligent?
abstract: The urothelium separates the urinary tract lumen from underlying tissues of the tract wall. Previously considered as merely an effective barrier between these two compartments it is now recognized as a more active tissue that senses and transduces information about physical and chemical conditions within the urinary tract, such as luminal pressure, urine composition, etc. To understand this sensory function it is useful to consider the urothelium and suburothelium as a functional unit; containing uroepithelial cells, afferent and efferent nerve fibers and suburothelial interstitial cells. This structure responds to alterations in its external environment through the release of diffusible agents, such as ATP and acetylcholine, and eventually modulates the activity of afferent nerves and underlying smooth muscles. This review considers different stresses the urothelium/suburothelium responds to; the particular chemicals released; the cellular receptors that are consequently affected; and how nerve and muscle function is modulated. Brief consideration is also to regional differences in the urothelium/suburothelium along the urinary tract. The importance of different pathways in relaying sensory information in the normal urinary tract, or whether they are significant only in pathological conditions is also discussed. An operational definition of intelligence is used, whereby a system (urothelium/suburothelium) responds to external changes, to maximize the possibility of the urinary tract achieving its normal function. If so, the urothelium can be regarded as intelligent. The advantage of this approach is that input–output functions can be mathematically formulated, and the importance of different components contributing to abnormal urinary tract function can be calculated. Neurourol.  2010.

title: Urothelial signaling.
abstract: The urothelium, which lines the inner surface of the renal pelvis, the ureters, and the urinary bladder, not only forms a high-resistance barrier to ion, solute and water flux, and pathogens, but also functions as an integral part of a sensory web which receives, amplifies, and transmits information about its external milieu. Urothelial cells have the ability to sense changes in their extracellular environment, and respond to chemical, mechanical and thermal stimuli by releasing various factors such as ATP, nitric oxide, and acetylcholine. They express a variety of receptors and ion channels, including P2X3 purinergic receptors, nicotinic and muscarinic receptors, and TRP channels, which all have been implicated in urothelial-neuronal interactions, and involved in signals that via components in the underlying lamina propria, such as interstitial cells, can be amplified and conveyed to nerves, detrusor muscle cells, and ultimately the central nervous system. The specialized anatomy of the urothelium and underlying structures, and the possible communication mechanisms from urothelial cells to various cell types within the bladder wall are described. Changes in the urothelium/lamina propria ("mucosa") produced by different bladder disorders are discussed, as well as the mucosa as a target for therapeutic interventions.

title: Nervous network for lower urinary tract function
abstract: Traditionally, sensory signaling in the urinary bladder has been largely attributed to direct activation of bladder afferents. There is substantive evidence that sensory systems can be influenced by non‐neuronal cells, such as the urothelium, which are able to respond to various types of stimuli that can include physiological, psychological and disease‐related factors. The corresponding release of chemical mediators (through activation of a number of receptors/ion channels) can initiate signaling mechanisms between and within urothelial cells, as well as other cell types within the bladder wall including bladder nerves. However, the mechanisms underlying how various cell types in the bladder wall respond to normal filling and emptying, and are challenged by a variety of stressors (physical and chemical) are still not well understood. Alterations or defects in signaling mechanisms are likely to contribute to the pathophysiology of bladder disease with symptoms including urinary urgency, increased voiding frequency and pain. This review will discuss some of the components involved in control of lower urinary tract function, with an emphasis on the sensor and transducer roles of the urothelium.

title: Lamina propria: The functional center of the bladder?
abstract: The bladder mucosa consists of the urothelium, basement membrane, and lamina propria (LP). Although the urothelium has been given much attention, it may be regarded as one part of a signaling system involving another equally important component of the bladder mucosa, namely, the LP. The LP lies between the basement membrane of the mucosa and the detrusor muscle and is composed of an extracellular matrix containing several types of cells, including fibroblasts, adipocytes, interstitial cells, and afferent and efferent nerve endings. In addition, the LP contains a rich vascular network, lymphatic vessels, elastic fibers, and smooth muscle fascicles (muscularis mucosae). The roles of the LP and its components in bladder function have not been definitively established, though it has been suggested to be the capacitance layer of the bladder, determining bladder compliance and enabling adaptive changes to increasing volumes. However, the bladder LP may also serve as a communication center, with an important integrative role in signal transduction to the central nervous system (nociception, mechanosensation). The LP may also, by means of its different components, make it possible for the urothelium to transmit information to other components of the bladder wall, contributing to activation of the detrusor muscle. In addition, the LP may serve as a source for production of factors influencing the growth of both the overlying urothelium and the underlying detrusor muscle. Neurourol. Urodynam. 33:9–16, 2014.

title: Integrative control of the lower urinary tract: preclinical perspective.
abstract: Storage and periodic expulsion of urine is regulated by a neural control system in the brain and spinal cord that coordinates the reciprocal activity of two functional units in the lower urinary tract (LUT): (a) a reservoir (the urinary bladder) and (b) an outlet (bladder neck, urethra and striated muscles of the urethral sphincter). Control of the bladder and urethral outlet is dependent on three sets of peripheral nerves: parasympathetic, sympathetic and somatic nerves that contain afferent as well as efferent pathways. Afferent neurons innervating the bladder have A-delta or C-fibre axons. Urine storage reflexes are organized in the spinal cord, whereas voiding reflexes are mediated by a spinobulbospinal pathway passing through a coordination centre (the pontine micturition centre) located in the brainstem. Storage and voiding reflexes are activated by mechanosensitive A-delta afferents that respond to bladder distension. Many neurotransmitters including acetylcholine, norepinephrine, dopamine, serotonin, excitatory and inhibitory amino acids, adenosine triphosphate, nitric oxide and neuropeptides are involved in the neural control of the LUT. Injuries or diseases of the nervous system as well as disorders of the peripheral organs can produce LUT dysfunctions including: (1) urinary frequency, urgency and incontinence or (2) inefficient voiding and urinary retention. Neurogenic detrusor overactivity is triggered by C-fibre bladder afferent axons, many of which terminate in the close proximity to the urothelium. The urothelial cells exhibit 'neuron-like' properties that allow them to respond to mechanical and chemical stimuli and to release transmitters that can modulate the activity of afferent nerves.

title: Physiological and pathological regulation of the autonomic control of urinary bladder contractility.
abstract: The urinary bladder stores urine for most of the day, a process facilitated by beta-adrenergic receptor-mediated detrusor relaxation and alpha(1)-adrenergic receptor-mediated contraction of the bladder neck. Physiological voiding is caused by detrusor contraction induced by muscarinic receptor stimulation. This manuscript reviews data on alterations of alpha(1)- and beta-adrenergic and of muscarinic responsiveness of the detrusor related to gender, developmental maturation, ageing and pathophysiological conditions such as diabetes, arterial hypertension and bladder outlet obstruction, all of which can be associated with alterations of bladder function such as bladder overactivity. The existing data show that none of the conditions associated with bladder overactivity exhibit increased muscarinic receptor responsiveness which could explain the clinical observations; while not being fully consistent, they if anything show a reduced responsiveness. On the other hand, more limited data demonstrate that alpha(1)-adrenergic responsiveness may be enhanced and beta-adrenergic responsiveness reduced in states associated with bladder overactivity. However, the existing data are too sparse and/or too inconsistent to allow definitive conclusions. Thus, alterations distinct from those of autonomic receptors may be better candidates to explain bladder dysfunction.

title: Neural control of the lower urinary tract: Peripheral and spinal mechanisms
abstract: This review deals with individual components regulating the neural control of the urinary bladder. This article will focus on factors and processes involved in the two modes of operation of the bladder: storage and elimination. Topics included in this review include: (1) The urothelium and its roles in sensor and transducer functions including interactions with other cell types within the bladder wall (“sensory web”), (2) The location and properties of bladder afferents including factors involved in regulating afferent sensitization, (3) The neural control of the pelvic floor muscle and pharmacology of urethral and anal sphincters (focusing on monoamine pathways), (4) Efferent pathways to the urinary bladder, and (5) Abnormalities in bladder function including mechanisms underlying comorbid disorders associated with bladder pain syndrome and incontinence. Neurourol. Urodynam. 29: 128–139, 2010.

title: Organization of the neural switching circuitry underlying reflex micturition
abstract: The functions of the lower urinary tract to store and periodically eliminate urine are regulated by a complex neural control system in the brain and spinal cord that coordinates the activity of the bladder and urethral outlet. Experimental studies in animals indicate that urine storage is modulated by reflex mechanisms in the spinal cord, whereas voiding is mediated by a spinobulbospinal pathway passing through a coordination centre in the rostral brain stem. Many of the neural circuits controlling micturition exhibit switch‐like patterns of activity that turn on and off in an all‐or‐none manner. This study summarizes the anatomy and physiology of the spinal and supraspinal micturition switching circuitry and describes a computer model of these circuits that mimics the switching functions of the bladder and urethra at the onset of micturition.

title: Autonomic nervous control of the urinary bladder
abstract: The autonomic nervous system plays an important role in the regulation of the urinary bladder function. Under physiological circumstances, noradrenaline, acting mainly on β3‐adrenoceptors in the detrusor and on α1A‐adrenoceptors in the bladder outflow tract, promotes urine storage, whereas neuronally released acetylcholine acting mainly on M3 receptors promotes bladder emptying. Under pathophysiological conditions, however, this system may change in several ways. Firstly, there may be plasticity at the levels of innervation and receptor expression and function. Secondly, non‐neuronal acetylcholine synthesis and release from the urothelium may occur during the storage phase, leading to a concomitant exposure of detrusor smooth muscle, urothelium and afferent nerves to acetylcholine and noradrenaline. This can cause interactions between the adrenergic and cholinergic system, which have been studied mostly at the post‐junctional smooth muscle level until now. The implications of such plasticity are being discussed.

title: Differential susceptibility to ageing of rat preganglionic neurones projecting to the major pelvic ganglion and of their afferent inputs
abstract: We have analysed age-related changes in the morphology of preganglionic neurones in the lumbosacral spinal cord, labelled following injection of retrograde tracers into the major pelvic ganglion of young adult and aged male rats. We have also examined changes in neurotransmitter-characterised spinal afferent inputs to these neurones, or to the nuclei in which they lie, using light and electron microscope immunohistochemistry. In previous investigations of the major pelvic ganglion, the sympathetic, but not parasympathetic, postganglionic neurones were seen to exhibit age-related changes and the same pattern is seen in the preganglionic neurones. This included an apparent reduction in the numbers of sympathetic preganglionic neurones, and a reduction in the length of their dendrites and the complexity of their branches. Ultrastructural immunohistochemical studies described here reveal significant reductions in the area of synaptic contact made by glutamate-immunoreactive boutons onto the dendrites of sympathetic (but not parasympathetic) preganglionic neurones, while contacts from boutons immunoreactive for glycine or gamma-aminobutyric acid (GABA) were unchanged. There is also a reduction in synaptic contacts received by sympathetic somata from boutons immunoreactive for none of these amino acids. Serotonin-immunoreactive terminals are closely associated with preganglionic autonomic neurones, and these are reduced in number in sympathetic, but not parasympathetic, spinal nuclei of aged rats. However, serial section electron microscopy has so far failed to demonstrate conventional synaptic contacts between serotonergic terminals and the dendrites or somata of the preganglionic autonomic neurones. In young animals, axon terminals immunoreactive for thyrotropin-releasing hormone (TRH) are abundant in all spinal laminae including area X, but in aged animals, such terminals are significantly reduced in number in regions containing preganglionic sympathetic, but not parasympathetic, neurones. These results indicate that the sympathetic preganglionic neuron populations that project to the major pelvic ganglion, and the spinal inputs they receive, show a number of degenerative changes in aged rats which are not seen parasympathetic preganglionic neuronal populations.

title: Age-associated changes in distribution of the P2X2 receptor in the major pelvic ganglion of the male rat.
abstract: P2X purinoceptors constitute a group of ligand-gated ion channels one of which, the P2X2 receptor has previously been described in neurons within autonomic ganglia, including the major pelvic ganglion (MPG). Earlier work strongly suggests that age-associated attrition of sympathetic but not parasympathetic MPG neurons occurs but there have been no investigations of age-related changes in P2X2 receptor expression in autonomic ganglia or to determine whether the receptor is localised in one or both of the two MPG neuronal subpopulations. In the current study, immunocytochemistry was employed to label cells expressing the P2X2 receptor in the MPG from young and aged male Wistar rats. By combining P2X2 receptor immunocytochemistry with the immunolocalisation of tyrosine hydroxylase (TH), the numbers of sympathetic (TH+) and parasympathetic (TH-) neurons expressing the P2X2 receptor were determined. In young rats P2X2 receptor expression was found in 93.08+/-3.2% of TH- (parasympathetic) neurons. In aged rats a similar analysis revealed no significant difference in the number of TH- neurons expressing the P2X2 receptor. In contrast a significant increase in the number of TH+ sympathetic neurons expressing P2X2 was observed in the MPG of aged rats (10.70+/-2.26%) in comparison to the young group (2.38+/-0.78%). Age-related changes in the numbers of small intensely fluorescent (SIF) cells which were highly P2X2 positive were also quantified, revealing a small reduction in number with age. This study has demonstrated the preferential localisation of P2X2 receptors to parasympathetic MPG neurons and suggests that purinergic transmission in the pelvic organs maybe largely unaffected by ageing.

title: Distribution of afferent axons in the bladder of rats
abstract: The distribution of afferent axons in the bladder of rats was studied by means of immunohistochemistry for calcitonin gene-related peptide (CGRP), in frozen sections and in wholemount preparations of mucosa and muscle coat. Synaptophysin-immunofluorescence was used for the general detection of all intramural axons. The afferent axons were distributed over four distinct targets: at the base of the epithelium, inside the epithelium, on blood vessels (both arteries and veins) and along muscle bundles. In the mucosa, all the afferent axons, except the perivascular ones, lay either inside the epithelium or in a subepithelial plexus very close to the basal surface of the epithelium. The plexus was thickest in the neck of the bladder and in the initial portion of the urethra, and it became progressively less dense in the adjacent regions; it did not extend beyond the equatorial region, and therefore the mucosa of the cranial region of the bladder had no afferent axons. Most of the axons in the subepithelial plexus were terminal axons and included conspicuous varicosities arranged in very long chains; branching points were numerous, usually at right angles and located at the level of a varicosity; some axons split and then rejoined, forming closed axonal loops. The afferent innervation of the musculature was more diffuse, and appeared uniform throughout the bladder. After unilateral surgical denervation (by excision of the pelvic ganglion 5–7 days earlier) areas of complete denervation were observed, but there were large areas where the innervation was only reduced. The results showed that there is a bilateral innervation of many regions of the mucosa and the musculature, including individual muscle bundles. A substantial number of fibres crossed the midline into the contralateral side of the bladder. CGRP-immunofluorescence in mucosal afferent axons is enhanced in the surviving axons 5 days after contralateral denervation, a change which is interpreted as an early sign of regeneration.

title: Neurophysiology of micturition and continence.
abstract: This article reviews the neuroanatomy, neurophysiology, and neuropharmacology involved in micturition and continence. Knowledge of these topics helps the clinician diagnose and treat voiding disorders that are caused by disease, trauma, drugs, and aging.

title: Neural control of the female urethral and anal rhabdosphincters and pelvic floor muscles.
abstract: The urethral rhabdosphincter and pelvic floor muscles are important in maintenance of urinary continence and in preventing descent of pelvic organs [i.e., pelvic organ prolapse (POP)]. Despite its clinical importance and complexity, a comprehensive review of neural control of the rhabdosphincter and pelvic floor muscles is lacking. The present review places historical and recent basic science findings on neural control into the context of functional anatomy of the pelvic muscles and their coordination with visceral function and correlates basic science findings with clinical findings when possible. This review briefly describes the striated muscles of the pelvis and then provides details on the peripheral innervation and, in particular, the contributions of the pudendal and levator ani nerves to the function of the various pelvic muscles. The locations and unique phenotypic characteristics of rhabdosphincter motor neurons located in Onuf's nucleus, and levator ani motor neurons located diffusely in the sacral ventral horn, are provided along with the locations and phenotypes of primary afferent neurons that convey sensory information from these muscles. Spinal and supraspinal pathways mediating excitatory and inhibitory inputs to the motor neurons are described; the relative contributions of the nerves to urethral function and their involvement in POP and incontinence are discussed. Finally, a detailed summary of the neurochemical anatomy of Onuf's nucleus and the pharmacological control of the rhabdosphincter are provided.

title: Sexual dimorphism and the influence of neonatal androgen in the dorsolateral motor nucleus of the rat lumbar spinal cord
abstract: There is a sexually dimorphic motor nucleus, the spinal nucleus of the bulbocavernosus (SNB) in the fifth and sixth lumbar segments of the rat spinal cord. We now report a second sex difference in the dorsolateral nucleus (DLN) in the ventral horn of the rat lumbar cord, which includes motoneurons innervating the ischiocavernosus muscle, a sexually dimorphic perineal muscle. Adult females possess fewer motoneurons in the DLN, probably because of an absence of neurons innervating the ischiocavernosus muscle, which females lack. The effect of a single dose of testosterone propionate on day 2 of life was confined to a specific rostrocaudal region of the adult DLN in which it partially masculinized the female DLN. Masculinized females have more DLN neurons than control females. The direction of change induced in DLN neuron number by the neonatal hormone treatment is compatible with the hypothesis that androgens are involved with the sexually dimorphic development of the DLN. In another motor nucleus, the retrodorsolateral nucleus, a small sex difference in neuron number was found in one study, but was not replicated in a second experiment.

title: The organization of the pudendal nerve in the male and female rat
abstract: Mature male and female Sprague‐Dawley rats were used in this study to compare the organization of the pudendal nerve in the two sexes. Experiments included (1) incubating the cut pudendal nerve in diamidino‐2‐phenylindole HCl (DAPI), fast blue (FB), or horseradish peroxidase (HRP) and (2) injecting individual perineal muscles with these substances. In both sexes, incubation of the pudendal nerve labelled two motoneuron nuclei in the L5‐L6 segments of the spinal cord. These nuclei are the dorsomedial (DM) and dorsolateral (DL) cell columns described by Schrϕder ( 1980). In agreement with previous studies, there were significantly more neurons in both nuclei in the male than in the female and the neurons were larger in the male. In both sexes, the DL and DM nuclei were characterized by a longitudinal dendritic structure. The DM nucleus also had numerous dendritic bundles extending across the midline, linking the DM nuclei bilaterally.

title: Ageing reduces the number of vesicular glutamate transporter 2 containing immunoreactive inputs to identified rat pelvic motoneurons
abstract: The immunocytochemical localisation of vesicular glutamate transporters, VGLUT1 and VGLUT2, was employed to identify putative glutamatergic axon terminals innervating pelvic motoneurons. VGLUT1 terminals were sparsely distributed within lumbosacral spinal motoneuron pools, including the dorsolateral nucleus, retrodorsolateral nucleus and spinal nucleus of the bulbospongiosus. This was in marked contrast to VGLUT2 which was expressed in a robust innervation of these areas. Retrograde tracing was used to reveal motoneurons innervating the levator ani (LA) muscle. On these neurons, associations with VGLUT2 immunoreactive terminals were abundant while those with VGLUT1 were rare. Ultrastructural investigations revealed that VGLUT2 immunoreactive terminals made asymmetric synaptic contacts with dendrites of retrogradely labelled LA motoneurons. Quantification of VGLUT2 immunoreactive boutons in close association with these dendrites was carried out in young and aged animals using light microscopy. This revealed a significant decline in the numbers of VGLUT2 immunoreactive boutons on the more distal dendrites of motoneurons in aged rats. VGLUT2 boutons were reduced by approximately 21% from 11.25+/-0.5 per 35-mum length of dendrite in young rats to 8.89+/-0.5 in aged animals. This decline in glutamatergic input may reduce the excitability of LA motoneurons and consequently decrease the capacity of the rat to induce reflexive erections.

title: Nuclear expression of PG-21, SRC-1, and pCREB in regions of the lumbosacral spinal cord involved in pelvic innervation in young adult and aged rats
abstract: In rats, ageing results in dysfunctional patterns of micturition and diminished sexual reflexes that may reflect degenerative changes within spinal circuitry. In both sexes the dorsal lateral nucleus and the spinal nucleus of the bulbospongiosus, which lie in the L5-S1 spinal segments, contain motor neurons that innervate perineal muscles, and the external anal and urethral sphincters. Neurons in the sacral parasympathetic nucleus of these segments provide autonomic control of the bladder, cervix and penis and other lower urinary tract structures. Interneurons in the dorsal gray commissure and dorsal horn have also been implicated in lower urinary tract function. This study investigates the cellular localisation of PG-21 androgen receptors, steroid receptor co-activator one (SRC-1) and the phosphorylated form of c-AMP response element binding protein (pCREB) within these spinal nuclei. These are components of signalling pathways that mediate cellular responses to steroid hormones and neurotrophins. Nuclear expression of PG-21 androgen receptors, SRC-1 and pCREB in young and aged rats was quantified using immunohistochemistry. There was a reduction in the number of spinal neurons expressing these molecules in the aged males while in aged females, SRC-1 and pCREB expression was largely unchanged. This suggests that the observed age-related changes may be linked to declining testosterone levels. Acute testosterone therapy restored expression of PG-21 androgen receptor in aged and orchidectomised male rats, however levels of re-expression varied within different nuclei suggesting a more prolonged period of hormone replacement may be required for full restoration.

title: The micturition switch and its forebrain influences
abstract: Dr DeGroat and Wickens has reviewed the central neural mechanisms controlling the lower urinary tract with a major focus on the brain stem circuitry that mediates the switch‐like characteristics of micturition, in particular the periaqueductal grey and the pontine micturition centre (de 2012). The review culminates in a computer model of how the brainstem switch operates in animals in which forebrain influences on micturition have been removed by decerebration. In this complementary paper, we review the mechanisms of forebrain involvement in the voluntary control of human micturition and the maintenance of continence with evidence based heavily on the results of functional brain imaging experiments.

title: Anatomy of the Central Neural Pathways Controlling the Lower Urinary Tract
abstract: This paper will review the central nervous control of the lower urinary tract.  Neuroanatomical, electrophysiological and pharmacological techniques have provided information about the neural circuitry and the neurotransmitters involved in the neural control of voiding.  Storage of urine is dependent in part upon spinal reflex mechanisms that activate sympathetic and somatic pathways to the urethral outlet as well as tonic inhibitory systems in the brain that suppress the parasympathetic outflow to the urinary bladder. Voiding is mediated by inhibition of sympathetic and somatic reflex pathways and activation of a spinobulbospinal parasympathetic reflex pathway passing through a micturition center in the rostral pons. Studies in animals indicate that glutamic acid is the major excitatory transmitter in the micturition reflex pathway and that a number of other transmitter mechanisms (noradrenergic, dopaminergic and GABAergic) modulate glutamatergic transmission. Damage to the brain or spinal cord can induce bladder hyperactivity by reducing central inhibitory mechanisms or by promoting a reorganization of spinal reflex pathways.  The central nervous regulation of the lower urinary tract is mediated by simple on-off switching circuits in the brain and spinal cord that are under voluntary control. Interruption of central inhibitory mechanisms can unmask primitive voiding reflexes that trigger bladder hyperactivity.

title: Cerebral control of the lower urinary tract: How age-related changes might predispose to urge incontinence
abstract: Loss of bladder control (urge incontinence) is common in elderly; the cause is usually unknown. Functional imaging has revealed the brain network controlling responses to bladder filling. Age-related changes in this network might predispose to urge incontinence. We sought such changes in 10 continent, healthy women aged 30-79 years who underwent fMRI while fluid (approximately 20 ml) was repeatedly infused into and withdrawn from the bladder. Data were collected in 4 measurement blocks with progressively increasing bladder volumes and were analyzed by SPM2, using the contrast infuse-withdraw to quantify response to bladder infusion. Effective connectivity was examined by physiophysiological interaction (PhPI; see interpretation in Supplementary Material), with right insula (RI) and dorsal anterior cingulate cortex (dACC) as seed regions. Dependence on age and bladder volume (= block number) was assessed. Bladder infusion evoked expected activations. Activation decreased with age in bilateral insula and dACC. PhPI revealed connectivity with RI and dACC in regions that included bilateral putamen and R pontine micturition center. Interaction (connectivity) tended to increase with age in regions including L insula, L paracentral lobule and PAG. Consistent with a special role in maintaining continence, medial prefrontal cortex (mPFC) showed a trend to deactivation on bladder infusion that became more prominent in old age, and a trend to negative interaction (connectivity) that weakened significantly with age. Thus, with increasing age, weaker signals in the bladder control network as a whole and/or changes in mPFC function or connecting pathways may be responsible for the development of urge incontinence.

title: Neural control of the lower urinary and gastrointestinal tracts: Supraspinal CNS mechanisms
abstract: Normal urinary function is contingent upon a complex hierarchy of CNS regulation. Lower urinary tract afferents synapse in the dorsal horn of the spinal cord and ascend to the midbrain periaqueductal gray (PAG), with a separate nociception path to the thalamus. A spino‐thalamo‐cortical sensory pathway is present in some primates, including humans. In the brainstem, the pontine micturition center (PMC) is a convergence point of multiple influences, representing a co‐ordinating center for voiding. Many PMC neurones have characteristics necessary to categorize the center as a pre‐motor micturition nucleus. In the lateral pontine brainstem, a separate region has some characteristics to suggest a “continence center.” Cerebral control determines that voiding is permitted if necessary, socially acceptable and in a safe setting. The frontal cortex is crucial for decision making in an emotional and social context. The anterior cingulate gyrus and insula co‐ordinate processes of autonomic arousal and visceral sensation. The influence of these centers on the PMC is primarily mediated via the PAG, which also integrates bladder sensory information, thereby moderating voiding and storage of urine, and the transition between the two phases. The parabrachial nucleus in the pons is also important in behavioral motivation of waste evacuation. Lower urinary tract afferents can be modulated at multiple levels by corticolimbic centers, determining the interoception of physiological condition and the consequent emotional motor responses. Alterations in cognitive modulation, descending modulation, and hypervigilance are important in functional (symptom‐based) clinical disorders. Neurourol. Urodynam. 29: 119–127, 2010.

title: Supraspinal Control of Urine Storage and Micturition in Men—An fMRI Study
abstract: Despite the crucial role of the brain in the control of the human lower urinary tract, little is known about the supraspinal mechanisms regulating micturition. To investigate the central regulatory mechanisms activated during micturition initiation and actual micturition, we used an alternating sequence of micturition imitation/imagination, micturition initiation, and actual micturition in 22 healthy males undergoing functional magnetic resonance imaging. Subjects able to micturate (voiders) showed the most prominent supraspinal activity during the final phase of micturition initiation whereas actual micturition was associated with significantly less such activity. Initiation of micturition in voiders induced significant activity in the brainstem (periaqueductal gray, pons), insula, thalamus, prefrontal cortex, parietal operculum and cingulate cortex with significant functional connectivity between the forebrain and parietal operculum. Subjects unable to micturate (nonvoiders) showed less robust activation during initiation of micturition, with activity in the forebrain and brainstem particularly lacking. Our findings suggest that micturition is controlled by a specific supraspinal network which is essential for the voluntary initiation of micturition. Once this network triggers the bulbospinal micturition reflex via brainstem centers, micturition continues automatically without further supraspinal input. Unsuccessful micturition is characterized by a failure to activate the periaqueductal gray and pons during initiation.

title: Afferent nerve regulation of bladder function in health and disease.
abstract: The afferent innervation of the urinary bladder consists primarily of small myelinated (Adelta) and unmyelinated (C-fiber) axons that respond to chemical and mechanical stimuli. Immunochemical studies indicate that bladder afferent neurons synthesize several putative neurotransmitters, including neuropeptides, glutamic acid, aspartic acid, and nitric oxide. The afferent neurons also express various types of receptors and ion channels, including transient receptor potential channels, purinergic, muscarinic, endothelin, neurotrophic factor, and estrogen receptors. Patch-clamp recordings in dissociated bladder afferent neurons and recordings of bladder afferent nerve activity have revealed that activation of many of these receptors enhances neuronal excitability. Afferent nerves can respond to chemicals present in urine as well as chemicals released in the bladder wall from nerves, smooth muscle, inflammatory cells, and epithelial cells lining the bladder lumen. Pathological conditions alter the chemical and electrical properties of bladder afferent pathways, leading to urinary urgency, increased voiding frequency, nocturia, urinary incontinence, and pain. Neurotrophic factors have been implicated in the pathophysiological mechanisms underlying the sensitization of bladder afferent nerves. Neurotoxins such as capsaicin, resiniferatoxin, and botulinum neurotoxin that target sensory nerves are useful in treating disorders of the lower urinary tract.

title: Localization of the micturition reflex center at dorsolateral pontine tegmentum of the rat
abstract: Various electrolytic lesions have been made to elucidate the 'micturition reflex center' at the rat dorsolateral pontine tegmentum. The bilateral lesion occupying the caudal part of nucleus tegmentalis laterodorsalis (TLD)( *) caused the urinary disorders. However, they could not be observed after the bilateral destruction of locus coeruleus.

title: Bilateral projections of the pontine micturition center to the sacral parasympathetic nucleus in the rat
abstract: Previous work has revealed that pontine micturition center (PMC) neurons send projections to the sacral parasympathetic nucleus (SPN) of the intermediolateral (IML) regions of L6-S1 spinal cord segments in rats. Although unilateral SPN injections will retrogradely label PMC neurons bilaterally, it is not known whether single PMC neurons project bilaterally to the SPN. There may be two different populations of PMC neurons on each side of the brainstem, with both groups independently connecting to the SPNs on opposite sides of the spinal cord. To verify one of these alternatives, a small injection of either rhodamine-labeled latex microspheres or a red fluorescent emulsion was made into the SPN on one side of the cord; a similar injection of either fluorescein-tagged microspheres or a green fluorescent emulsion was made into the other. After at least seven days, the rats were perfused. Inspection of 40 micron cord sections confirmed the similar placement of these injections along the rostrocaudal axis of the cord and that no tracer had spread across midline. Thirty-micron brain sections were examined for filled neurons. Red, green and double labeled neurons were found bilaterally in the PMC, subcoeruleus, and A5 regions. Although some red nucleus cells were also filled, they were only singly labeled and always located contralateral to the injection. Finally, immunohistochemical staining of dopamine-beta-hydroxylase (DBH) containing cells confirmed that some labeled cells were also noradrenergic. We therefore conclude that some PMC, subcoeruleus, and A5 neurons send axons to the SPN on both sides of the lumbosacral cord.

title: Distinct intrinsic and synaptic properties of pre‐sympathetic and pre‐parasympathetic output neurons in Barrington's nucleus
abstract: Barrington's nucleus (BN), commonly known as the pontine micturition center, controls micturition and other visceral functions through projections to the spinal cord. In this study, we developed a rat brain slice preparation to determine the intrinsic and synaptic mechanisms regulating pre‐sympathetic output (PSO) and pre‐parasympathetic output (PPO) neurons in the BN using patch‐clamp recordings. The PSO and PPO neurons were retrogradely labeled by injecting fluorescent tracers into the intermediolateral region of the spinal cord at T13‐L1 and S1‐S2 levels, respectively. There were significantly more PPO than PSO neurons within the BN. The basal activity and membrane potential were significantly lower in PPO than in PSO neurons, and A‐type K+ currents were significantly larger in PPO than in PSO neurons. Blocking A‐type K+ channels increased the excitability more in PPO than in PSO neurons. Stimulting μ‐opioid receptors inhibited firing in both PPO and PSO neurons. The glutamatergic EPSC frequency was much lower, whereas the glycinergic IPSC frequency was much higher, in PPO than in PSO neurons. Although blocking GABAA receptors increased the excitability of both PSO and PPO neurons, blocking glycine receptors increased the firing activity of PPO neurons only. Furthermore, blocking ionotropic glutamate receptors decreased the excitability of PSO neurons but paradoxically increased the firing activity of PPO neurons by reducing glycinergic input. Our findings indicate that the membrane and synaptic properties of PSO and PPO neurons in the BN are distinctly different. This information improves our understanding of the neural circuitry and central mechanisms regulating the bladder and other visceral organs.

title: Central pathways controlling micturition and urinary continence.
abstract: The central control of micturition and urinary continence in cats and humans is organized in a similar manner. In cats, 4 areas in the brainstem and diencephalon are implicated in the control of micturition: (1) the pontine micturition center or Barrington area directly excites bladder motoneurons in the sacral cord during micturition; at the same time, it inhibits indirectly, via inhibitory gamma-aminobutyric acidergic and glycinergic interneurons in the medial sacral cord, the external urethral sphincter motoneurons; (2) the pontine continence center activates the external urethral sphincter motoneurons during continence; (3) the midbrain periaqueductal gray receives bladder filling information; and (4) the hypothalamus, in the beginning of micturition. According to positron emission tomography studies, in humans, the same supraspinal regions are active during micturition. Furthermore, the human cingulate and prefrontal cortices are activated during both micturition and continence, indicating that these areas are important for the onset of micturition, but not for the reflex itself. The primary motor cortex of the pelvic floor is important for voluntary pelvic floor contraction, but it is not involved in normal urinary continence.

title: Evidence for corticotropin‐releasing hormone projections from Barrington's nucleus to the periaqueductal gray and dorsal motor nucleus of the vagus in the rat
abstract: The present study used anterograde and retrograde tract tracing and immunohistochemistry to determine the efferent projections of corticotropin‐releasing hormone (CRH) neurons of Barrington's nucleus in the rat. Injections of Phaseolus vulgaris‐leucoagglutinin into Barrington's nucleus resulted in anterograde labeling in the dorsal motor nucleus of the vagus, periaqueductal gray, medial thalamic nuclei, lateral hypothalamus, paraventricular nucleus of the hypothalamus, lateral preoptic area, and lateral septum. The retrograde tract tracer, fluorogold, injected into the lumbosacral spinal cord labeled many, but not all, CRH‐immunoreactive neurons in Barrington's nucleus. Moreover, some Barrington's neurons that were retrogradely labeled from the spinal cord were not CRH‐immunoreactive. Several CRH‐immunoreactive Barrington's neurons were retrogradely labeled by fluorogold injections into the periaqueductal gray, and these were located predominantly in the dorsal part of the nucleus. Additionally, some CRH‐immunoreactive Barrington's neurons were retrogradely labeled from fluorogold injections into the dorsal motor nucleus of the vagus. In contrast, fluorogold injections into the lateral hypothalamus, lateral preoptic area, or lateral septum did not result in double labeling of CRH‐immunoreactive neurons in Barrington's nucleus. These results suggest that many, but not all, CRH‐containing neurons of Barrington's nucleus project to the lumbosacral spinal cord. In addition to their previously documented projections to the spinal cord, these neurons may be a source of CRH in the periaqueductal gray and dorsal motor nucleus of the vagus. CRH projections of Barrington's nucleus may play a role in behavioral or autonomic aspects of stress responses, in addition to their proposed role in micturition.

title: Evidence for divergent projections to the brain noradrenergic system and the spinal parasympathetic system from Barrington's nucleus
abstract: The present study was designed to determine whether Barrington's nucleus, which lies ventromedial to the locus coeruleus (LC) and projects to the sacral parasympathetic nucleus, is a source of afferent projections to the LC. Restricted injections of the anterograde tracer, biocytin, into Barrington's nucleus labeled varicose fibers that extended from the injection site into the LC. Consistent with this, injections of the retrograde tracers, wheatgerm agglutinin conjugated to horseradish peroxidase coupled to gold particles (WGA-Au-HRP) or fluorescein-conjugated latex beads, into the LC labeled numerous (approximately 10%) Barrington's neurons that were also retrogradely labeled by Fluoro-Gold (FG) injections in the spinal cord. Retrograde tracing from the LC combined with corticotropin-releasing hormone (CRH) immunohistochemistry revealed that at least one third of the retrogradely labeled neurons in Barrington's nucleus were CRH-immunoreactive (CRH-IR). Finally, in triple labeling studies, CRH-Barrington's neurons were consistently observed that were retrogradely labeled from both the and spinal cord. These findings implicate Barrington's nucleus as an LC afferent and a source of CRH-IR fibers in the LC. Additionally, the results suggest that some Barrington's neurons diverge to innervate both the spinal cord and the LC. This divergent innervation may serve to coregulate the sacral parasympathetic nervous system and brain noradrenergic system, thus providing a mechanism for coordinating pelvic visceral functions with forebrain activity.

title: Distribution of locus coeruleus axons in the rat spinal cord: a combined anterograde transport and immunohistochemical study
abstract: The distribution of locus coeruleus axons in the rat spinal cord was studied by anterograde transport of Phaseolus vulgaris leucoagglutinin in combination with dopamine-beta-hydroxylase immunohistochemistry. Locus coeruleus axons were observed primarily in the superficial laminae of the dorsal horn. Few locus coeruleus fibers were seen in the vicinity of motoneuron pools or in the intermediolateral cell column of the thoracic spinal cord. The results of this study suggest a selective action of the coeruleo-spinal projection upon sensory inputs to the spinal cord.

title: The noradrenergic neurotoxin DSP-4 eliminates the coeruleospinal projection but spares projections of the A5 and A7 groups to the ventral horn of the rat spinal cord
abstract: Systemic administration of the noradrenergic neurotoxin DSP-4 results in a complete loss of staining of noradrenergic (NA) axons in the dorsal horn and intermediate zone of the rat spinal cord. NA axon staining in the ventral horn and in the intermediolateral cell column is only slightly decreased by the drug treatment. We have taken advantage of this differential effect of DSP-4 on NA axons to determine the location and number of cells that give rise to NA axons in the ventral horn and the intermediolateral cell column. Retrograde transport of the fluorescent tracer True blue was combined with dopamine-beta-hydroxylase immunohistochemistry 2 weeks after treatment of rats with 50 mg/kg of DSP-4. Compared with controls, the drug treatment resulted in a more than 90% decrease in the number of retrogradely labeled NA neurons in the locus coeruleus and an only 30– 50% reduction in the number of retrogradely labeled NA cells in the A5 and A7 groups. The results reveal different sites of termination in the spinal cord of NA axons originating in the LC and in NA cells of the A5 and A7 groups: the LC distributes fibers mainly to the dorsal horn and the intermediate zone, while NA cells of the A5 and A7 groups project to motoneurons of the ventral horn and the intermediolateral cell column.

title: Age-associated changes in the monoaminergic innervation of rat lumbosacral spinal cord
abstract: The effects of ageing on the innervation patterns of lumbosacral spinal nuclei involved in controlling lower urinary tract functions, including micturition, were studied using immunohistochemistry for serotonin (5-HT) and tyrosine hydroxylase (TH) in male Wistar rats of 3 and 24 months. Quantitative image analysis revealed significant age-associated declines in the innervation of most regions including the intermediolateral cell nucleus, sacral parasympathetic nucleus, dorsal grey commissure and in the ventral horn including the dorsolateral nucleus which in the rat is one of the component nuclei homologous to Onuf's nucleus in man. Notable exceptions to this generalised decline were observed in the 5-HT innervation of the sacral parasympathetic nucleus, which was maintained, and in the region of the dorsolateral motor nucleus where TH-like immunoreactivity did not significantly decline. These results suggest that the changes in micturition characteristics observed in aged rats may in part be a consequence of the alterations in, and decline of, aminergic inputs to both autonomic and somatic spinal nuclei associated with bladder function.

title: Mediation of micturition reflex by central norepinephrine from the locus coeruleus in the cat.
abstract: We examined whether norepinephrine originating in the locus coeruleus mediates the micturition reflex in anesthetized cats. 6-Hydroxydopamine, a catecholamine neurotoxin, injected bilaterally into the locus coeruleus markedly decreased catecholamine fluorescence in the lesioned area and induced urinary retention after 72 to 84 hr. At this time, there was no or only slight contraction of the urinary bladder induced by its distension, while the contraction was noted before the treatment. However, phenylephrine, an alpha 1-receptor agonist, applied intrathecally in 6-hydroxydopamine-treated animals induced moderate bladder contraction. In sham-operated animals, the bladder contraction on its distension was inhibited by intrathecally applied prazosin, an alpha 1-receptor antagonist. Thus, in the micturition reflex, norepinephrine derived from the locus coeruleus acts on the alpha 1-adrenergic receptors in the sacral cord, and induces urinary bladder contraction via activation of the sacral parasympathetic preganglionic neurons.

title: Serotonin and norepinephrine involvement in efferent pathways to the urethral rhabdosphincter: implications for treating stress urinary incontinence.
abstract: Stress urinary incontinence (SUI), the most common form of incontinence, continues to be a largely underdiagnosed problem that imposes large financial and quality-of-life burdens on many women but has few treatment options. Ongoing animal and early human studies have shown that monoamine neurotransmitters play key roles in controlling urethral storage and micturition reflexes. Motor neurons found in the Onuf nucleus of the sacral spinal cord control urethral function, and have several unique properties that distinguish them from other motor neurons. First, the neurons are uniformly smaller than other surrounding motor neurons and have bundled dendrites, allowing strong synchronous activation or inhibition. Second, the neurons demonstrate unique neurochemical profiles. Unlike neurons in surrounding areas, the motor neurons of the Onuf nucleus have dense populations of noradrenergic and serotonergic terminals. Animal studies have shown that alpha1-adrenoceptors and serotonin (5-hydroxytryptamine [5-HT]) receptors in the Onuf nucleus facilitate sphincter contraction. Agonists that stimulate these receptors facilitate the guarding or incontinence reflex, whereas antagonists that block the receptors inhibit this reflex. Therefore, boosting the effects of 5-HT and norepinephrine (NE) to enhance sphincter activity could be clinically promising for improving the symptoms of SUI. Importantly, the activity of the sphincter neurons can be increased pharmacologically during urine storage without interfering with bladder-sphincter synergy. Administering the 5-HT/NE uptake inhibitor duloxetine facilitates sphincter contraction during bladder filling but not during bladder contraction in micturition. This unique effect of duloxetine may be maintained by the selective neuromodulatory effects of 5-HT and NE on activation of sphincter motor neurons by the neurotransmitter glutamate. Prolonging the effect of naturally released NE and 5-HT with duloxetine could augment the body's normal processes for controlling urine storage and micturition. Early trials have demonstrated that duloxetine significantly reduces incontinence episodes and is well tolerated in the clinical setting.

title: Changes in the substance P-containing innervation of the lumbosacral spinal cord in male Wistar rats as a consequence of ageing
abstract: Quantitative image analysis was used to determine age-related changes in the substance P-containing innervation of autonomic and somatic nuclei in the lumbosacral spinal cord, which are associated with the control of micturition and sexual reflexes. In the upper lumbar segments (L1-L2), significant declines in the distribution density of substance P-containing processes were observed in the dorsal grey commissure, the intermediolateral cell column and the ventral horn. More caudally, at levels corresponding to L5 through S1, significant reductions were seen in the dorsal grey commissure and within the sacral parasympathetic nucleus. In contrast to these observations, the substance P-immunoreactive innervation of the dorsolateral nucleus remained robust in aged animals and was not significantly different from young adults. It is possible that these distinct age-related patterns of change in substance P-containing innervation, are reflected in the urinary/sexual dysfunction's in aged animals.

title: The aging bladder—a significant but underestimated role in the development of lower urinary tract symptoms
abstract: There are three major areas in which bladder dysfunction causes considerable losses in quality of life: detrusor instability, impaired detrusor function and detrusor reaction on bladder outlet obstruction. Considerable changes in detrusor morphology, detrusor innervation and bladder metabolism are seen with aging and obstruction. This causes dysfunction and lower urinary tract symptoms. The relation between aging per se and external influence on the detrusor from diseases in the nervous system, in the vascular supply and in the lower urinary tract itself is poorly understood. To improve our ability to prevent and treat these conditions we need more insight in these pathophysiological conditions.

title: The aging bladder.
abstract: Although it is well established that lower urinary tract symptoms increase in frequency with aging, there are few studies of the mechanisms that underlie bladder dysfunction. Age-related reduction in bladder capacity, uninhibited contractions, decreased urinary flow rate, diminished urethral pressure profile, and increased postvoid residual volume warrant investigation and require differentiation between symptoms associated with aging and those related to comorbid conditions. Here, the current data are reviewed, including those from muscle bath investigations of bladder tissue contractility, in vivo studies using animal models, and clinical studies in the aging population.

title: Aging and the underactive detrusor: A failure of activity or activation?
abstract: To examine the known and potential contributions of motor, sensory, and biomechanical dysfunctions to the clinical problems of detrusor underactivity and detrusor hyperactivity/impaired contractility.

title: Impaired bladder function in aging male rats.
abstract: The prevalence of bladder dysfunctions increases with age. In humans it is difficult to separate changes related to exogenous factors from those directly related to the aging process. Some confounding variables can be avoided by studying age related changes in an animal model. We evaluated the impact of age on bladder function in vivo and in vitro, and characterized the corresponding morphological changes.



Young (4 to 6 months old) and old (older than 28 to 30 months) male Fischer/Brown Norway rats were used in the study. Cystometric studies were done in conscious, freely moving rats. After cystometry tissue strips from the bladder body were used in in vitro studies of muscarinic receptor activation and electrical field stimulation, and histological examination.



Old rats had higher bladder weight than young rats but the bladder-to-body weight ratio did not change. We noted significant age related differences in 8 of 10 cystometric parameters. Old rats had increased bladder capacity, post-void residual volume, micturition volume and frequency, baseline and intermicturition pressure, and spontaneous activity but decreased micturition pressure. Bladder strip responses to carbachol and electrical field stimulation were significantly lower in old than in young rats. Histological examination revealed urothelial thinning, lower muscle mass and higher collagen content in the bladders of old vs young rats.



Physiological aging alters bladder function in male rats even when external factors remain constant. Thus, in old rats bladder capacity, post-void residual urine and spontaneous activity are higher, and responses to muscarinic receptor stimulation and electrical field stimulation are lower than in young rats. Such changes correspond to findings in aging human bladders, supporting the view that the Fischer/Brown Norway rat is a useful model in which to study age related bladder function changes.

title: Aging impairs neurogenic contraction in guinea pig urinary bladder: role of oxidative stress and melatonin.
abstract: The incidence of urinary bladder disturbances increases with age, and free radical accumulation has been proposed as a causal factor. Here we investigated the association between changes in bladder neuromuscular function and oxidative stress in aging and the possible benefits of melatonin treatment. Neuromuscular function was assessed by electrical field stimulation (EFS) of isolated guinea pig detrusor strips from adult and aged female guinea pigs. A group of adult and aged animals were treated with 2.5 mg x kg(-1) x day(-1) melatonin for 28 days. Neurotransmitter blockers were used to dissect pharmacologically the EFS-elicited contractile response. EFS induced a neurogenic and frequency-dependent contraction that was impaired by aging. This impairment is in part related to a decrease in detrusor myogenic contractility. Age also decreased the sensitivity of the contraction to pharmacological blockade of purinergic and sensitive fibers but increased the effect of blockade of nitrergic and adrenergic nerves. The density of cholinergic and nitrergic nerves remained unaltered, but aging modified afferent fibers. These changes were associated with an increased level of markers for oxidative stress. Melatonin treatment normalized oxidative levels and counteracted the aging-associated changes in bladder neuromuscular function. In conclusion, these results show that aging modifies neurogenic contraction and the functional profile of the urinary bladder plexus and simultaneously increases the oxidative damage to the organ. Melatonin reduces oxidative stress and improves the age-induced changes in bladder neuromuscular function, which could be of importance in reducing the impact of age-related bladder disorders.

title: Melatonin restores impaired contractility in aged guinea pig urinary bladder
abstract: Urinary bladder disturbances are frequent in the elderly population but the responsible mechanisms are poorly understood. This study evaluates the effects of aging on detrusor myogenic contractile responses and the impact of melatonin treatment. The contractility of bladder strips from adult, aged and melatonin‐treated guinea pigs was evaluated by isometric tension recordings. Cytoplasmatic calcium concentration ([Ca2+]i) was estimated by epifluorescence microscopy of fura‐2‐loaded isolated detrusor smooth muscle cells, and the levels of protein expression and phosphorylation were quantitated by Western blotting. Aging impairs the contractile response of detrusor strips to cholinergic and purinergic agonists and to membrane depolarization. The impaired contractility correlates with increased [Ca2+]i in response to the stimuli, suggesting a reduced Ca2+sensitivity. Indeed, the agonist‐induced contractions in adult strips were sensitive to blockade with Y27362, an inhibitor of Rho kinase (ROCK) and GF109203X, an inhibitor of protein kinase C (PKC), but these inhibitors had negligible effects in aged strips. The reduced Ca2+ sensitivity in aged tissues correlated with lower levels of RhoA, ROCK, PKC and the two effectors CPI‐17 and MYPT1, and with the absence of CPI‐17 and MYPT1 phosphorylation in response to agonists. Interestingly, melatonin treatment restored impaired contractility via normalization of Ca2+ handling and Ca2+ sensitizations pathways. Moreover, the indoleamine restored age‐induced changes in oxidative stress and mitochondrial polarity. These results suggest that melatonin might be a novel therapeutic tool to palliate aging‐related urinary bladder contractile impairment.

title: Muscarinic stimulation of the mouse isolated whole bladder: physiological responses in young and ageing mice.
abstract: 1 Peripheral autonomous bladder activity is an incompletely understood property that may be important both in normal bladder function and in functional problems of the lower urinary tract. We describe how a muscarinic agonist, arecaidine, influences intravesical pressure and intramural bladder contractions in the isolated mouse and how response varies in ageing mice. 2 A group of 12 mice aged 3-4 months was compared with an 'ageing' group of 12 mice age 28-34 months. Bladders were microsurgically removed and mounted in whole organ tissue baths. The effects of the muscarinic agonist arecaidine on intravesical pressure and intramural contractions were performed at different bladder volumes. 3 In normal mice, arecaidine elicited tonic and phasic contractions, the latter showing a more substantial increase in amplitude with bladder distension. Localized 'micromotion' contractions were seen in the bladder wall, with regional differences arising after exposure to arecaidine. A background release of acetylcholine was inferred from the pressure increase induced by the cholinesterase inhibitor physostigmine. 4 Both micromotion activity and the phasic component of the arecaidine response were substantially reduced in ageing mice; the tonic component was preserved in the same specimens. 5 We conclude that the enhanced pressure fluctuations seen at high bladder volumes may act as a peripheral determinant of bladder capacity, and that changes in such activity may contribute to altered functional capacity and lower urinary tract symptoms in ageing individuals.

title: Aging differentially modifies agonist-evoked mouse detrusor contraction and calcium signals
abstract: Although aging-induced changes in urinary bladder neurotransmission have been studied in some detail, information regarding alterations in detrusor muscle is scanty and addresses only partial aspects of the myogenic response of detrusor. Rodent bladder aging shows several features similar to those reported in humans. The aim of this study was to characterize in aged mouse the alterations of detrusor muscle contraction and the putative underlying changes in Ca2+ signals. We studied in vitro the myogenic contraction induced by agonists in detrusor strips from adult (3 months old) or aged (23–25 months old) mice. In addition, we determined the agonist-induced [Ca2+]i signals by epifluorescence microscopy in fura-2 loaded isolated detrusor cells. Aging impaired the contractile response of bladder strips to cholinergic stimulation with bethanechol and to chemical depolarization with KCl-containing solutions. On the contrary, the response to purinergic stimulation (ATP) was enhanced. Aging also diminished the transient Ca2+ signal evoked by bethanechol and the Ca2+ influx induced by KCl in bladder strips. Treatments aimed to release calcium from intracellular stores (caffeine and a low level of ionomycin in Ca2+-free medium) showed that aging reduces the size of agonist-releasable stores. Similar to contraction, the mobilization of Ca2+ by ATP was increased in aged cells. Therefore, the differential effects of aging on detrusor contraction are associated to alterations of [Ca2+]i signals: the cholinergic inhibition is due to inhibition of voltage-operated Ca2+ influx and reduction of the size of intracellular Ca2+ stores, while the age-induced ATP response is accompanied by an enhanced Ca2+ mobilization.

title: Localized contractions in the normal human bladder and in urinary urgency
abstract: To describe an observational study to establish whether localized activity arises in the normal human bladder, and whether there is any correspondence between changes in such activity and reported sensation.

title: Detrusor expulsive strength is preserved, but responsiveness to bladder filling and urinary sensitivity is diminished in the aging mouse.
abstract: The prevalence of urinary symptoms increases with age and is a significant source of distress, morbidity, and expense in the elderly. Recent evidence suggests that symptoms in the aged may result from sensory dysfunction, rather than abnormalities of detrusor performance. Therefore, we employed a pressure/flow multichannel urethane-anesthetized mouse cystometry model to test the hypothesis that in vivo detrusor performance does not degrade with aging. Secondarily, we sought to evaluate sensory responsiveness to volume using pressure-volume data generated during bladder filling. Cystometric data from 2-, 12-, 22-, and 26-mo-old female C57BL6 mice were compared. All 2- and 12-mo-old mice, 66% of 22-mo-old mice, and 50% of 26-mo-old mice responded to continuous bladder filling with periodic reflex voiding. Abdominal wall contraction with voiding had a minimal contribution to expulsive pressure, whereas compliance pressure was a significant contributor. Maximum bladder pressure, estimated detrusor pressure, detrusor impulse (pressure-time integral), as well as indices of detrusor power and work, did not decrease with aging. Bladder precontraction pressures decreased, compliance increased, and nonvoiding contraction counts did not change with increasing age. Intervoid intervals, per-void volumes, and voiding flow rates increased with age. Calculations approximating wall stress during filling suggested loss of bladder volume sensitivity with increasing age. We conclude that aging is associated with an impaired ability to respond to the challenge of continuous bladder filling with cyclic voiding, yet among responsive animals, voiding detrusor contraction strength does not degrade with aging in this murine model. Furthermore, indirect measures suggest that bladder volume sensitivity is diminished. Thus, changes in homeostatic reserve and peripheral and/or central sensory mechanisms may be important contributors to aging-associated changes in bladder function.

title: Structural basis of geriatric voiding dysfunction. II. Aging detrusor: normal versus impaired contractility.
abstract: Little information on the structural norm of the aging detrusor is currently available. To gain insight into the pathophysiology of geriatric voiding dysfunction, detrusor biopsies were examined by electron microscopy to identify structural correlates of specific, urodynamically defined abnormalities of vesical function in 35 elderly subjects. Prospective urodynamic grouping of the subjects and segregation of the detrusor specimens by ultrastructural features were done independently and blindly. One structural pattern so identified, the dense band pattern, matched the urodynamic group with neither detrusor overactivity nor bladder outlet obstruction. This neither group included 11 women and 2 men 65 to 91 years old (mean age 76 years). Except for 2 patients with minimal stress incontinence, all were symptom-free. None of the patients had diabetes or a neurological deficit. Urodynamically, 10 patients had impaired and 3 had normal detrusor contractility. The dense band structural pattern was characterized by overall normal configuration of muscle cells and cell junctions, sarcolemma (muscle cell membrane) dominated by dense bands with depleted caveolae in interposed zones and slight widening of spaces between muscle cells with little-collagen content. Specimens from the 10 subjects with impaired contractility displayed, in addition, widespread degeneration of muscle cells and axons. The remaining 3 specimens, without degeneration, matched the subjects with normal contractility, who were continent and symptom-free. It is proposed that the dense band pattern represents the structural norm of aging detrusor, heralds a process of muscle cell de-differentiation in the detrusor accompanying natural aging, and may affect exchange and storage of ions involved in the excitation-contraction coupling mechanism of muscle cells through depletion of caveolae. Widespread degeneration of muscle cells and axons, superimposed on the dense band pattern, is proposed as the structural correlate of impaired detrusor contractility in the aging detrusor.

title: The aging bladder: morphology and urodynamics
abstract: Incontinence at any age is abnormal but, wrongfully, is often neglected or dismissed as a natural component of growing old by physicians or the older subjects themselves. Geriatric incontinence can rarely be attributed to a single cause [150]. Like incontinence at a younger age, it has established causes related to the lower urinary tract. Additional contributory factors, however, including other diseases and functional impairments, make the elderly particularly vulnerable to incontinence, although aging per se does not cause it [94, 156, 191].

title: Loss of bladder smooth muscle caveolae in the aging bladder
abstract: Caveolae are specialized regions of the cell membrane that modulate signal transduction and alterations in these structures affect bladder smooth muscle (BSM) contraction. Since bladder dysfunctions are common in the elderly, we evaluated the effect of aging on the morphology of caveolae and caveolin protein expression in BSM.

title: Sympathetic and sensory innervation of the urinary tract in young adult and aged rats: a semi-quantitative histochemical and immunohistochemical study
abstract: SummaryThe sympathetic innervation of the urinary tract of young adult (4 months) and aged (24+ months) rats has been examined by glyoxylic acid-induced fluorescence for the detection of noradrenaline and by immunofluorescence using antisera against tyrosine hydroxylase (TH) and neuropeptide Y (NPY). Immunostaining for calcitonin gene-related peptide (CGRP), known to be present in pelvic sensory nerves, was also performed. Semi-quantitative estimations of nerve densities were made of noradrenergic and peptidergic fibres innervating the smooth musculature of the ureter, bladder and urethra, and of the urinary tract vasculature. In the aged rats the overall patterns of innervation remained unchanged. However, with the exception of the vesical vasculature, the density of noradrenergic innervation decreased as did the intensity of histofluorescence. A similar pattern of results was observed by TH and NPY immunofluorescence. The results present evidence for a diminution in the sympathetic control of the urinary tract in aged rats. The pattern and density of CGRP-immunoreactive nerves was unchanged in the aged animals suggesting that pelvic visceral sensory innervation is more resistant to the effects of advancing age.

title: The enteric nervous system and neurogastroenterology
abstract: Neurogastroenterology is defined as neurology of the gastrointestinal tract, liver, gallbladder and pancreas and encompasses control of digestion through the enteric nervous system (ENS), the central nervous system (CNS) and integrative centers in sympathetic ganglia. This Review provides a broad overview of the field of neurogastroenterology, with a focus on the roles of the ENS in the control of the musculature of the gastrointestinal tract and transmucosal fluid movement. Digestion is controlled through the integration of multiple signals from the ENS and CNS; neural signals also pass between distinct gut regions to coordinate digestive activity. Moreover, neural and endocrine control of digestion is closely coordinated. Interestingly, the extent to which the ENS or CNS controls digestion differs considerably along the digestive tract. The importance of the ENS is emphasized by the life-threatening effects of certain ENS neuropathies, including Hirschsprung disease and Chagas disease. Other ENS disorders, such as esophageal achalasia and gastroparesis, cause varying degrees of dysfunction. The neurons in enteric reflex pathways use a wide range of chemical messengers that signal through an even wider range of receptors. These receptors provide many actual and potential targets for modifying digestive function.

title: Social Structure Predicts Genital Morphology in African Mole-Rats
abstract: African mole-rats (Bathyergidae, Rodentia) exhibit a wide range of social structures, from solitary to eusocial. We previously found a lack of sex differences in the external genitalia and morphology of the perineal muscles associated with the phallus in the eusocial naked mole-rat. This was quite surprising, as the external genitalia and perineal muscles are sexually dimorphic in all other mammals examined. We hypothesized that the lack of sex differences in naked mole-rats might be related to their unusual social structure.  We compared the genitalia and perineal muscles in three African mole-rat species: the naked mole-rat, the solitary silvery mole-rat, and the Damaraland mole-rat, a species considered to be eusocial, but with less reproductive skew than naked mole-rats. Our findings support a relationship between social structure, mating system, and sexual differentiation. Naked mole-rats lack sex differences in genitalia and perineal morphology, silvery mole-rats exhibit sex differences, and Damaraland mole-rats are intermediate.  The lack of sex differences in naked mole-rats is not an attribute of all African mole-rats, but appears to have evolved in relation to their unusual social structure and reproductive biology.

title: Relationship between interstitial cells of Cajal, fibroblast-like cells and inhibitory motor nerves in the internal anal sphincter
abstract: Interstitial cells of Cajal (ICC) have been shown to participate in nitrergic neurotransmission in various regions of the gastrointestinal (GI) tract. Recently, fibroblast-like cells, which are positive for platelet-derived growth factor receptor α (PDGFRα+), have been suggested to participate additionally in inhibitory neurotransmission in the GI tract. The distribution of ICC and PDGFRα+ cell populations and their relationship to inhibitory nerves within the mouse internal anal sphincter (IAS) are unknown. Immunohistochemical techniques and confocal microscopy were therefore used to examine the density and arrangement of ICC, PDGFRα+ cells and neuronal nitric-oxide-synthase-positive (nNOS+) nerve fibers in the IAS of wild-type (WT) and W/Wv mice. Of the total tissue volume within the IAS circular muscle layer, 18% consisted in highly branched PDGFRα+ cells (PDGFRα+-IM). Other populations of PDGFRα+ cells were observed within the submucosa and along the serosal and myenteric surfaces. Spindle-shaped intramuscular ICC (ICC-IM) were present in the WT mouse IAS but were largely absent from the W/Wv IAS. The ICC-IM volume (5% of tissue volume) in the WT mouse IAS was significantly smaller than that of PDGFRα+-IM. Stellate-shaped submucosal ICC (ICC-SM) were observed in the WT and W/Wv IAS. Minimum surface distance analysis revealed that nNOS+ nerve fibers were closely aligned with both ICC-IM and PDGFRα+-IM. An even closer association was seen between ICC-IM and PDGFRα+-IM. Thus, a close morphological arrangement exists between inhibitory motor neurons, ICC-IM and PDGFRα+-IM suggesting that some functional interaction occurs between them contributing to inhibitory neurotransmission in the IAS.

title: The physiology of continence and evacuation.
abstract: Continence is maintained by the coordinated function of the pelvic floor, rectum and anal sphincters. Evacuation occurs through a relaxed pelvic floor. The rectum acts to either store or expel stool both of which require cortical sensory awareness acting in conjunction with intramural and spinal reflexes that ensure timely defecation. The anal sphincters act individually and in unison in response to rectal distension and the sensation of rectal filling. Reflex relaxation of the internal anal sphincter has an additional sensory function in allowing sampling of rectal contents in the upper anal canal. Voluntary control of the external anal sphincter is key in the voluntary deferring of evacuation until a socially opportune moment. This review describes the physiological roles of each of these continence organs in order to understand the complex process of defecation.

title: The pharmacology of the internal anal sphincter and new treatments of ano‐rectal disorders
abstract: Surgical options for faecal incontinence in the presence of intact sphincters are limited. Furthermore, in patients with fissures, lateral sphincterotomy reduces anal sphincter hypertonia but there has been concern about complications. A greater understanding of the basic pharmacology of the internal anal sphincter has led to the development of novel treatments for both these disorders. A Medline review was undertaken for internal anal sphincter pharmacology, anal fissures and faecal incontinence. This review is based on these articles and those found by further cross‐referencing.  Nitric oxide released from non‐adrenergic non‐cholinergic nerves is the main inhibitory agent in the internal anal sphincter. Relaxations are also mediated through β‐adrenoceptors and muscarinic receptors. Stimulation of α‐receptors results in contraction. Calcium and its entry through L‐type calcium channels is important for the maintenance of tone. Nitric oxide donors produce reductions in resting anal tone and heal fissures but are associated with side‐effects. Muscarinic agents and calcium channel antagonists show promise as low side‐effect alternatives. Botulinum toxin appears more efficacious than other agents in healing fissures. To date, α‐receptor agonists have been disappointing at improving incontinence.

title: Pelvic floor: anatomy and function
abstract: The pelvic floor is a dome‐shaped striated muscular sheet that encloses the bladder, uterus, and rectum, and, together with the anal sphincters, has an important role in regulating storage and evacuation of urine and stool. This article reviews the anatomy, nerve supply, pharmacology, and functions of the anal sphincters and the pelvic floor. The internal and external anal sphincters are primarily responsible for maintaining faecal continence at rest and when continence is threatened, respectively. Defecation is a somato‐visceral reflex regulated by dual nerve supply (i.e. somatic and autonomic) to the anorectum. The net effects of sympathetic and cholinergic stimulation are to increase and reduce anal resting pressure, respectively. Faecal incontinence and functional defecatory disorders may result from structural changes and/or functional disturbances in the mechanisms of faecal continence and defecation.

title: Lower gastrointestinal functions
abstract: The human colon serves to absorb water and electrolytes, store intraluminal contents until elimination is socially convenient, and salvage nutrients by bacterial metabolism of carbohydrates that have not been absorbed in the small intestine. The anorectum is responsible for fecal continence and defecation. This article is a broad perspective of the current status and a personal perspective of future challenges in understanding lower gastrointestinal functions in health and disease in humans.

title: Neurogenic colorectal and pelvic floor dysfunction.
abstract: Constipation and faecal incontinence are common symptoms among patients with spinal cord injury (SCI), myelomeningocoele (MMC), multiple sclerosis (MS), Parkinson's disease (PD) and stroke. Faecal incontinence in SCI, MMC and MS is mainly due to abnormal rectosigmoid compliance and rectoanal reflexes, loss of rectoanal sensibility and loss of voluntary control of the external anal sphincter. Constipation in SCI, MMC and MS is probably due to immobilisation, abnormal colonic contractility, tone and rectoanal reflexes or side effects from medication. In PD, dystonia of the external anal sphincter causes difficult rectal evacuation and the loss of dopaminergic neurons in the enteric nervous system probably causes slow-transit constipation. Changes after stroke remain to be studied. Though dietary adjustments, oral laxatives, suppositories and other conservative treatment modalities are commonly used, evidence for their use in patients with central neurological disorders is scarce. For patients with severe symptoms trans-anal irrigation, the Malone appendicostomy or a colostomy can be recommended.

title: Basal internal anal sphincter tone, inhibitory neurotransmission, and other factors contributing to the maintenance of high pressures in the anal canal
abstract: Maintenance of the basal tone in the internal anal sphincter (IAS) is critical for rectoanal continence. Effective evacuation requires a fully functional rectoanal inhibitory reflex (RAIR)‐mediated relaxation of the IAS via inhibitory neurotransmission (INT). Systematic studies examining the nature of the INT in different species have identified nitric oxide (NO) as the major inhibitory neurotransmitter. However, other mediators such as vasoactive intestinal polypeptide (VIP), ATP, and carbon monoxide (CO) may also play species‐specific role under certain experimental conditions. Measurements of the intraluminal pressures in the IAS along with the force of the isolated IAS tissues are the mainstay in the basic studies for the molecular mechanisms underlying the basal tone and in the nature of the INT. The identification of NO as the inhibitory neurotransmitter has led to major advances in the diagnosis and treatment of a number of rectoanal motility disorders associated with the IAS dysfunction. Besides the IAS, the high pressures in the anal canal are affected by the external anal sphincter (EAS) function, and its malfunction may also lead to rectoanal incontinence. Different approaches including biofeedback have been attempted to improve the EAS function, with variable outcomes. There is a dire need for the innovative ways to improve the week high pressures zone in the anal canal. This viewpoint focuses on two studies that extend the above concept of multiplicity of inhibitory neurotransmitters (Neurogastroenterol Motil 2011 23 e11–25), and that high pressures in the anal canal can be improved by the EAS plication (Neurogastroenterol Motil 2011 23 70–5).

title: Structure and organization of interstitial cells of Cajal in the gastrointestinal tract
abstract: The morphological features of interstitial cells of Cajal (ICC) in the gastrointestinal (GI) tract are described based on observations of laboratory animals including mice, rats and guinea‐pigs, using immunohistochemical staining for Kit and electron microscopy. ICC show a specific distribution, arrangement and cell shape depending on their location within various regions and tissue layers of the GI tract. Hence they are classified into several subtypes. The stomach shows distinct regional variations in the distribution of subtypes of ICC from the cardia to pylorus, whereas the small intestine and colon both seem to retain nearly the same distribution pattern of subtypes of ICC throughout each organ. All subtypes of ICC share common ultrastructural features, such as the presence of numerous mitochondria, abundant intermediate filaments, and formation of gap junctions with the same type of cells and with smooth muscle cells. In addition, depending on their species and anatomical location, some subtypes of ICC show some features typical of smooth muscle cells including a basal lamina, caveolae, subsurface cisterns and dense bodies. ICC are somewhat heterogeneous morphologically. A question is raised on a special relationship between their ultrastructural features and dependency on Kit/stem cell factor system. As the neuromediator function of ICC, reciprocal distribution of ICC and gap junctions in the muscle coat is demonstrated by the comparison of Kit immunoreactive cells and gap junction protein connexin 43 in both small intestine and colon.

title: Changes in neuromuscular transmission in the W/Wv mouse internal anal sphincter
abstract: Intramuscular interstitial cells of Cajal (ICC‐IM) have been shown to participate in nitrergic neuromuscular transmission (NMT) in various regions of the gastrointestinal (GI) tract, but their role in the internal anal sphincter (IAS) is still uncertain. Contractile studies of the IAS in the W/Wv mouse (a model in which ICC‐IM numbers are markedly reduced) have reported that nitrergic NMT persists and that ICC‐IM are not required. However, neither the changes in electrical events underlying NMT nor the contributions of other non‐nitrergic neural pathways have been examined in this model.

title: Neuroeffector apparatus in gastrointestinal smooth muscle organs
abstract: Control of gastrointestinal (GI) movements by enteric motoneurons is critical for orderly processing of food, absorption of nutrients and elimination of wastes. Work over the past several years has suggested that motor neurotransmission is more complicated than simple release of transmitter from nerve terminals and binding of receptors on smooth muscle cells. In fact the ‘neuro‐effector’ junction in the tunica muscularis might consist of synaptic‐like connectivity with specialized cells, and contributions from multiple cell types in integrated post‐junctional responses. Interstitial cells of Cajal (ICC) were proposed as potential mediators in motor neurotransmission based on reduced post‐junctional responses observed in W mutants that have reduced populations of ICC. More recent studies on W mutants have contradicted the original findings, and suggested that ICC may not be significant players in motor neurotransmission. This review examines the evidence for and against the role of ICC in motor neurotransmission and outlines areas for additional investigation that would help further resolve this controversy.

title: Aging of the mammalian gastrointestinal tract: a complex organ system
abstract: Gastrointestinal disorders are a major cause of morbidity in the elderly population. The gastrointestinal tract is the most complex organ system; its diverse cells perform a range of functions essential to life, not only secretion, digestion, absorption and excretion, but also, very importantly, defence. The gastrointestinal tract acts not only as a barrier to harmful materials and pathogens but also contains the vast number of beneficial bacterial populations that make up the microbiota. Communication between the cells of the gastrointestinal tract and the central nervous and endocrine systems modifies behaviour; the organisms of the microbiota also contribute to this brain–gut–enteric microbiota axis. Age-related physiological changes in the gut are not only common, but also variable, and likely to be influenced by external factors as well as intrinsic aging of the cells involved. The cellular and molecular changes exhibited by the aging gut cells also vary. Aging intestinal smooth muscle cells exhibit a number of changes in the signalling pathways that regulate contraction. There is some evidence for age-associated degeneration of neurons and glia of the enteric nervous system, although enteric neuronal losses are likely not to be nearly as extensive as previously believed. Aging enteric neurons have been shown to exhibit a senescence-associated phenotype. Epithelial stem cells exhibit increased mitochondrial mutation in aging that affects their progeny in the mucosal epithelium. Changes to the microbiota and intestinal immune system during aging are likely to contribute to wider aging of the organism and are increasingly important areas of analysis. How changes of the different cell types of the gut during aging affect the numerous cellular interactions that are essential for normal gut functions will be important areas for future aging research.

title: Age-related changes in small intestinal mucosa epithelium architecture and epithelial tight junction in rat models
abstract: Background and aimsFunctions of the intestinal mucosal barrier are often impaired in the elderly and are closely associated with many age-related diseases. However, mechanisms by which aging influences intestinal barrier function still remain unclear. The aim of this study was to investigate age-related changes in small intestinal morphology, bacteria contents and expression of epithelial tight junction (TJ) proteins.MethodsThirty Sprague–Dawley rats were divided into groups: young (3 months), adult (12 months), and old (24 months). The small intestinal mucosal architecture and TJ of intestinal epithelial cells were examined by light microscopy and transmission electron microscopy. Jejunum and cecum contents were cultured to identify and measure bacterial species. mRNA expression of Zonula occludens-1 (ZO-1) and occludin were measured by semi-quantitative RT-PCR. Protein expression of ZO-1 and occludin were detected by immunohistochemistry and Western blot.ResultsNormal ileum villi, which were thick and regularly arranged, though increasingly scattered and atrophic in character with shorter and narrower dimensions (P < 0.01), were observed in old rats, along with an elevated number of Gram-positive and Gram-negative bacteria in the jejunum. The TJs of intestinal epithelial cells, as detected by transmission electron microscopy, were wider and discontinuous in old rats. Age-induced down-regulation of mRNA expression and decreased protein expression of ZO-1 and occludin were observed in the ileum (P < 0.01).ConclusionsOur study indicated that age-related intestinal barrier dysfunction may be associated with mucosal atrophy, damages to TJ structure, increased small intestine bacteria counts, and decreased epithelial TJ protein.

title: Age-associated remodeling of the intestinal epithelial barrier.
abstract: Disorders of the gastrointestinal tract are common in the elderly people; however, the precise trait(s) of aging that contribute to the vulnerability of the gastrointestinal tract are poorly understood. Recent evidence suggests that patients with gastrointestinal disorders have increased intestinal permeability. Here, we address the hypothesis that disruption of the intestinal barrier is associated with aging. Our results demonstrated that permeability was significantly higher in colonic biopsies collected from old baboons compared with young baboons. Additionally, colonic tissue from the older animals had decreased zonula occluden-1, occludin, and junctional adhesion molecule-A tight junction protein expression and increased claudin-2 expression. Upregulation of miR-29a and inflammatory cytokines IFN-γ, IL-6, and IL-1β was also found in colonic biopsies from old baboons relative to young baboons. These results show for the first time that a pivotal contributing factor to geriatric vulnerability to gastrointestinal dysfunction may be increased colonic permeability via age-associated remodeling of intestinal epithelial tight junction proteins.

title: Gut microbiota composition correlates with diet and health in the elderly
abstract: Alterations in intestinal microbiota composition are associated with several chronic conditions, including obesity and inflammatory diseases. The microbiota of older people displays greater inter-individual variation than that of younger adults. Here we show that the faecal microbiota composition from 178 elderly subjects formed groups, correlating with residence location in the community, day-hospital, rehabilitation or in long-term residential care. However, clustering of subjects by diet separated them by the same residence location and microbiota groupings. The separation of microbiota composition significantly correlated with measures of frailty, co-morbidity, nutritional status, markers of inflammation and with metabolites in faecal water. The individual microbiota of people in long-stay care was significantly less diverse than that of community dwellers. Loss of community-associated microbiota correlated with increased frailty. Collectively, the data support a relationship between diet, microbiota and health status, and indicate a role for diet-driven microbiota alterations in varying rates of health decline upon ageing.

title: Anatomical evidence for enteric neuroimmune interactions in Peyer’s patches
abstract: Peyer's patches (PP), a key component of the gut-associated lymphoid tissue, serve as the primary inductive sites for intestinal immunity. In the present study, we addressed the hypothesis that the morphological features of PP innervation are consistent with an immunomodulatory role for the enteric nervous system. Laser scanning confocal microscopy was used to collect images through large tissue volumes, yielding a three-dimensional perspective of the neuronal network superimposed on PP follicles from porcine jejunum and human ileum. Peptidergic nerve fibers were found in close apposition to immunocytes within PP subepithelial domes and the adjacent villi. The results suggest that nerve fibers in PP may participate in neuroimmune cross-talk within individual antigen-sampling sites as well as integrate information across multiple antigen-sampling sites.

title: Macrophages Associated with the Intrinsic and Extrinsic Autonomic Innervation of the Rat Gastrointestinal Tract
abstract: Interactions between macrophages and the autonomic innervation of gastrointestinal (GI) tract smooth muscle have received little experimental attention. To better understand this relationship, immunohistochemistry was performed on GI whole mounts from rats at three ages. The phenotypes, morphologies, and distributions of gut macrophages are consistent with the cells performing extensive housekeeping functions in the smooth muscle layers. Specifically, a dense population of macrophages was located throughout the muscle wall where they were distributed among the muscle fibers and along the vasculature. Macrophages were also associated with ganglia and connectives of the myenteric plexus and with the sympathetic innervation. Additionally, these cells were in tight registration with the dendrites and axons of the myenteric neurons as well as the varicosities along the length of the sympathetic axons, suggestive of a contribution by the macrophages to the homeostasis of both synapses and contacts between the various elements of the enteric circuitry. Similarly, macrophages were involved in the presumed elimination of neuropathies as indicated by their association with dystrophic neurons and neurites which are located throughout the myenteric plexus and smooth muscle wall of aged rats. Importantly, the patterns of macrophage-neuron interactions in the gut paralleled the much more extensively characterized interactions of macrophages (i.e., microglia) and neurons in the CNS. The present observations in the PNS as well as extrapolations from homologous microglia in the CNS suggest that GI macrophages play significant roles in maintaining the nervous system of the gut in the face of wear and tear, disease, and aging.

title: Glial cells in the gut
abstract: The enteric nervous system is composed of both neurons and glia. Recent evidence indicates that enteric glia–which vastly outnumber enteric neurons–are actively involved in the control of gastrointestinal functions: they contain neurotransmitter precursors, have the machinery for uptake and degradation of neuroligands, and express neurotransmitter‐receptors which makes them well suited as intermediaries in enteric neurotransmission and information processing in the ENS. Novel data further suggest that enteric glia have an important role in maintaining the integrity of the mucosal barrier of the gut. Finally, enteric glia may also serve as a link between the nervous and immune systems of the gut as indicated by their potential to synthesize cytokines, present antigen and respond to inflammatory insults. The role of enteric glia in human disease has not yet been systematically studied, but based on the available evidence it is predictable that enteric glia are involved in the etiopathogenesis of various pathological processes in the gut, particularly such with neuroinflammatory or neurodegenerative components.

title: Novel functional roles for enteric glia in the gastrointestinal tract
abstract: Enteric glia are a unique class of peripheral glial cells within the gastrointestinal tract. Major populations of enteric glia are found in enteric ganglia in the myenteric and submucosal plexuses of the enteric nervous system (ENS); these cells are also found outside of the ENS, within the circular muscle and in the lamina propria of the mucosa. These different populations of cells probably represent unique classes of glial cells with differing functions. In the past few years, enteric glia have been found to be involved in almost every gut function including motility, mucosal secretion and host defence. Subepithelial glia seem to have a trophic and supporting relationship with intestinal epithelial cells, but the necessity of these roles in the maintenance of normal epithelial functions remains to be shown. Likewise, glia within enteric ganglia are activated by synaptic stimulation, suggesting an active role in synaptic transmission, but the precise role of glial activation in normal enteric network activity is unclear. Excitingly, enteric glia can also give rise to new neurons, but seemingly only under limited circumstances. In this Review, we discuss the current body of evidence supporting functional roles of enteric glia and identify key gaps in our understanding of the physiology of these unique cells.

title: The digestive neuronal–glial–epithelial unit: a new actor in gut health and disease
abstract: The monolayer of columnar epithelial cells lining the gastrointestinal tract—the intestinal epithelial barrier (IEB)—is the largest exchange surface between the body and the external environment. The permeability of the IEB has a central role in the regulation of fluid and nutrient intake as well as in the control of the passage of pathogens. The functions of the IEB are highly regulated by luminal as well as internal components, such as bacteria or immune cells, respectively. Evidence indicates that two cell types of the enteric nervous system (ENS), namely enteric neurons and enteric glial cells, are potent modulators of IEB functions, giving rise to the novel concept of a digestive 'neuronal–glial–epithelial unit' akin to the neuronal–glial–endothelial unit in the brain. In this Review, we summarize findings demonstrating that the ENS is a key regulator of IEB function and is actively involved in pathologies associated with altered barrier function.

title: Enteric glia and neuroprotection: basic and clinical aspects.
abstract: The enteric nervous system (ENS), a major regulatory system for gastrointestinal function, is composed of neurons and enteric glial cells (EGCs). Enteric glia have long been thought to provide only structural support to neurons. However, recent evidence indicates enteric glia-neuron cross talk significantly contributes to neuronal maintenance, survival, and function. Thus damage to EGCs may trigger neurodegenerative processes thought to play a role in gastrointestinal dysfunctions and symptoms. The purpose of this review is to provide an update on EGCs, particularly focusing on their possible neuroprotective features and the resultant enteric neuron abnormalities subsequent to EGC damage. These neuroprotective mechanisms may have pathogenetic relevance in a variety of functional and inflammatory gut diseases. Basic and clinical (translational) studies support a neuroprotective role mediated by EGCs. Different models have been developed to test whether selective EGC damage/ablation has an impact on gut functions and the ENS. Preclinical data indicated that selective EGC alterations were associated with changes in gut physiology related to enteric neuron abnormalities. In humans, a substantial loss of EGCs was described in patients with various functional and/or inflammatory gastrointestinal diseases. However, whether EGC changes precede or follow neuronal degeneration and loss and how this damage occurs is not defined. Additional studies on EGC neuroprotective capacity are expected to improve knowledge of gut diseases and pave the way for targeted therapeutic strategies of underlying neuropathies.

title: Plasticity of pelvic autonomic ganglia and urogenital innervation.
abstract: Pelvic ganglia contain a mixture of sympathetic and parasympathetic neurons and provide most of the motor innervation of the urogenital organs. They show a remarkable sensitivity to androgens and estrogens, which impacts on their development into sexually dimorphic structures and provide an array of mechanisms by which plasticity of these neurons can occur during puberty and adulthood. The structure of pelvic ganglia varies widely among species, ranging from rodents, which have a pair of large ganglia, to humans, in whom pelvic ganglion neurons are distributed in a large, complex plexus. This plexus is frequently injured during pelvic surgical procedures, yet strategies for its repair have yet to be developed. Advances in this area will come from a better understanding of the effects of injury on the cellular signaling process in pelvic neurons and also the role of neurotrophic factors during development, maintenance, and repair of these axons.

title: MULTIPLE LEVELS OF SENSORY INTEGRATION IN THE INTRINSIC SENSORY NEURONS OF THE ENTERIC NERVOUS SYSTEM
abstract: 1. The enteric nervous system (ENS) is present in the wall of the gastrointestinal tract and contains all the functional classes of neuron required for complete reflex arcs. One of the most important and intriguing classes of neuron is that responsive to sensory stimuli: sensory neurons with cell bodies intrinsic to the ENS.

title: Nitric oxide not carbon monoxide mediates nonadrenergic noncholinergic relaxation in the murine internal anal sphincter.
abstract: Inhibitory reflexes in the internal anal sphincter (IAS) are controlled by inhibitory nonadrenergic, noncholinergic innervation (i-NANC). We investigated the roles of 3 different neurohumoral agonists as possible i-NANC neurotransmitters: carbon monoxide (CO), nitric oxide (NO), and vasoactive intestinal peptide (VIP).



IAS smooth muscle strips were isolated from wild-type (WT), heme oxygenase (HO)-2 knockout (HO-2-/-) and neuronal NO synthase (nNOS) knockout (nNOS-/-) mice. Relaxation of IAS was induced by CO, NO, VIP, and electrical field stimulation (EFS) in the presence and absence of neurohumoral inhibitors (tin protoporphyrin IX [SnPP IX] for CO synthesis, N(omega)-nitro-L-arginine [L-NNA] for NO synthesis, and VIP(10-28) for VIP receptor). Western blot and immunohistochemistry were used to test the presence and localization of HO (for CO synthesis) types 1 (HO-1) and 2 (HO-2), neuronal NO synthase (nNOS, for NO synthesis), and VIP.



All 3 neurohumoral agonists produced relaxation (with no difference between WT and HO-2-/- IAS), but CO was over 100 times less potent than NO and VIP. EFS produced relaxation in WT and HO-2-/- IAS with the same intensity. L-NNA and nNOS deletion (approximately 80%) and VIP(10-28) (approximately 15%) significantly inhibited the relaxations, whereas SnPP IX had no effect. Positive immunoreactivities for HO-2, nNOS, and VIP were found in the myenteric plexus of WT IAS. HO-2-/- IAS did not express immunoreactivity for HO-2.



i-NANC relaxations of mouse IAS are primarily mediated via NO (by nNOS activity) and partly via VIP. CO directly relaxes the mouse IAS but does not play any significant role in the i-NANC relaxation.

title: Distinct roles of nitric oxide synthases and interstitial cells of Cajal in rectoanal relaxation.
abstract: Nitric oxide (NO) relaxes the internal anal sphincter (IAS), but its enzymatic source(s) remains unknown; neuronal (nNOS) and endothelial (eNOS) NO synthase (NOS) isoforms could be involved. Also, interstitial cells of Cajal (ICC) may be involved in IAS relaxation. We studied the relative roles of nNOS, eNOS, and c-Kit-expressing ICC for IAS relaxation using genetic murine models. The basal IAS tone and the rectoanal inhibitory reflex (RAIR) were assessed in vivo by a purpose-built solid-state manometric probe and by using wild-type, nNOS-deficient (nNOS-/-), eNOS-deficient (eNOS-/-), and W/W(v) mice (lacking certain c-Kit-expressing ICC) with or without L-arginine or N(omega)-nitro-L-arginine methyl ester (L-NAME) treatment. Moreover, the basal tone and response to electrical field stimulation (EFS) were studied in organ bath using wild-type and mutant IAS. In vivo, the basal tone of eNOS-/- was higher and W/W(v) was lower than wild-type and nNOS-/- mice. L-arginine administered rectally, but not intravenously, decreased the basal tone in wild-type, nNOS-/-, and W/W(v) mice. However, neither L-arginine nor L-NAME affected basal tone in eNOS-/- mice. In vitro, L-arginine decreased basal tone in wild-type and nNOS-/- IAS but not in eNOS-/- or wild-type IAS without mucosa. The in vivo RAIR was intact in wild-type, eNOS-/-, and W/W(v) mice but absent in all nNOS-/- mice. EFS-induced IAS relaxation was also reduced in nNOS-/- IAS. Thus the basal IAS tone is largely controlled by eNOS in the mucosa, whereas the RAIR is controlled by nNOS. c-Kit-expressing ICC may not be essential for the RAIR.

title: Functional evidence for purinergic inhibitory neuromuscular transmission in the mouse internal anal sphincter.
abstract: The neurotransmitter(s) underlying nitric oxide synthase (NOS)-independent neural inhibition in the internal anal sphincter (IAS) is still uncertain. The present study investigated the role of purinergic transmission. Contractile and electrical responses to electrical field stimulation of nerves (0.1-5 Hz for 10-60 s) were recorded in strips of mouse IAS. A single stimulus generated a 28-mV fast inhibitory junction potential (IJP) and relaxation. The NOS inhibitor N(omega)-nitro-l-arginine (l-NNA) reduced the fast IJP duration by 20%. Repetitive stimulation at 2.5-5 Hz caused a more sustained IJP and sustained relaxation. l-NNA reduced relaxation at 1 Hz and the sustained IJP at 2.5-5 Hz. All other experiments were carried out in the presence of NOS blockade. IJPs and relaxation were significantly reduced by the P2 receptor antagonists 4-[[4-formyl-5-hydroxy-6-methyl-3-[(phosphonooxy)methyl]-2-pyridinyl]azo]-1,3-benzenedisulfonic acid (PPADS) (100 microM), by desensitization of P2Y receptors with adenosine 5'-[beta-thio]diphosphate (ADP-betaS) (10 microM), and by the selective P2Y1 receptor blocker 2'-deoxy-N(6)-methyl adenosine 3',5'-diphosphate (MRS2179) (10 microM). Relaxation and IJPs were also significantly reduced by the K(+) channel blocker apamin (1 microM). Removal of extracellular potassium (K(o)) increased IJP amplitude to 205% of control, whereas return of K(o) 30 min later hyperpolarized cells by 19 mV and reduced IJP amplitude to 50% of control. Exogenous ATP (3 mM) relaxed muscles in the presence of TTX (1 microM) and hyperpolarized cells by 15 mV. In conclusion, these data suggest that purinergic transmission significantly contributes to NOS-independent neural inhibition in the mouse IAS. P2Y1 receptors, as well as at least one other P2 receptor subtype, contribute to this pathway. Purinergic receptors activate apamin-sensitive K(+) channels as well as other apamin-insensitive conductances leading to hyperpolarization and relaxation.

title: Functional role of vasoactive intestinal polypeptide in inhibitory motor innervation in the mouse internal anal sphincter
abstract: Vasoactive intestinal polypeptide (VIP)‐ergic neuromuscular transmission (NMT) was examined in the internal anal sphincter of wild‐type mice and compared with that of VIP−/− mice. Relaxation and hyperpolarization during brief trains of electrical field stimulation (EFS; 4 s) were mediated by purinergic and nitrergic NMT. During longer stimulus trains, a non‐purinergic, non‐nitrergic (NNNP) relaxation and hyperpolarization slowly developed and persisted for several minutes beyond the end of the stimulus train. The NNNP NMT was abolished by VIP receptor antagonists, absent in the VIP−/− mouse internal anal sphincter and mimicked by exogenous VIP. These data suggest that NNNP NMT gives rise to ultraslow relaxation and hyperpolarization that is mediated by VIP. In vivo, this pathway may be activated with larger rectal distensions, leading to a more prolonged anal relaxation.

title: Interstitial cells of Cajal are involved in the afferent limb of the rectoanal inhibitory reflex
abstract: Interstitial cells of Cajal (ICC) have been shown to be involved in nitrergic neurotransmission of the lower oesophageal sphincter and pylorus. Here we studied the role of ICC and nitric oxide (NO) in the inhibitory neurotransmission of the murine internal anal sphincter (IAS).  The rectoanal inhibitory reflex, rectal compliance, and relaxation of the isolated IAS to electrical stimulation were measured in controls, KIT W/KIT Wv mice, and neuronal NO synthase (nNOS) deficient mice. In addition, we evaluated the effect of blockade of nNOS using N-nitro-L-arginine methyl ester. Distribution of nNOS positive neurones and ICC in the IAS was assessed immunohistochemically.  KIT positive ICC were present in a dense network in the IAS of controls but not in KIT W/KITWv mice. Relaxation of IAS muscle strips induced by electrical stimulation was diminished in nNOS−/− mice but not in KIT W/KIT Wv mice. Blockade of NOS reduced the relaxation of IAS muscle strips in both mice. Relaxation of the IAS to rectal distension was significantly diminished in KIT W/KIT Wv mice and nNOS deficient mice. In concert, in vivo blockade of NOS attenuated the relaxation of the IAS in controls. No significant difference in compliance was found.  The inhibitory innervation of the IAS and the rectoanal inhibitory reflex are mediated by NO and the rectoanal inhibitory reflex requires an intact network of ICC in the IAS. Thus both loss of nitrergic innervation and deficiency of ICC lead to impaired anal relaxation and may play an important role in rectal evacuation disorders.

title: Neural regulation of intestinal nutrient absorption
abstract: The nervous system and the gastrointestinal (GI) tract share several common features including reciprocal interconnections and several neurotransmitters and peptides known as gut peptides, neuropeptides or hormones. The processes of digestion, secretion of digestive enzymes and then absorption are regulated by the neuro-endocrine system. Luminal glucose enhances its own absorption through a neuronal reflex that involves capsaicin sensitive primary afferent (CSPA) fibres. Absorbed glucose stimulates insulin release that activates hepatoenteric neural pathways leading to an increase in the expression of glucose transporters. Adrenergic innervation increases glucose absorption through α1 and β receptors and decreases absorption through activation of α2 receptors. The vagus nerve plays an important role in the regulation of diurnal variation in transporter expression and in anticipation to food intake. Vagal CSPAs exert tonic inhibitory effects on amino acid absorption. It also plays an important role in the mediation of the inhibitory effect of intestinal amino acids on their own absorption at the level of proximal or distal segment. However, chronic extrinsic denervation leads to a decrease in intestinal amino acid absorption. Conversely, adrenergic agonists as well as activation of CSPA fibres enhance peptides uptake through the peptide transporter PEPT1. Finally, intestinal innervation plays a minimal role in the absorption of fat digestion products. Intestinal absorption of nutrients is a basic vital mechanism that depends essentially on the function of intestinal mucosa. However, intrinsic and extrinsic neural mechanisms that rely on several redundant loops are involved in immediate and long-term control of the outcome of intestinal function.

title: Constipation in neurological diseases
abstract: Hippocrates noted that “it is a general rule, that intestines become sluggish with age”, though the precise mechanisms for this association remains uncertain even today.

title: Age-related changes in vagal afferents innervating the gastrointestinal tract
abstract: Recent progress in understanding visceral afferents, some of it reviewed in the present issue, serves to underscore how little is known about the aging of the visceral afferents in the gastrointestinal (GI) tract. In spite of the clinical importance of the issue-with age, GI function often becomes severely compromised-only a few initial observations on age-related structural changes of visceral afferents are available. Primary afferent cell bodies in both the nodose ganglia and dorsal root ganglia lose Nissl material and accumulate lipofucsin, inclusions, aggregates, and tangles. Additionally, in changes that we focus on in the present review, vagal visceral afferent terminals in both the muscle wall and the mucosa of the GI tract exhibit age-related structural changes. In aged animals, both of the vagal terminal types examined, namely intraganglionic laminar endings and villus afferents, exhibit dystrophic or regressive morphological changes. These neuropathies are associated with age-related changes in the structural integrity of the target organs of the affected afferents, suggesting that local changes in trophic environment may give rise to the aging of GI innervation. Given the clinical relevance of GI tract aging, a more complete understanding both of how aging alters the innervation of the gut and of how such changes might be mitigated should be made research priorities.

title: Brain–gut connections in functional GI disorders: anatomic and physiologic relationships
abstract: Understanding the neural regulation of gut function and sensation makes it easier to understand the interrelatedness of emotionality, symptom‐attentive behavior or hypervigilance, gut function and pain. The gut and the brain are highly integrated and communicate in a bidirectional fashion largely through the ANS and HPA axis. Within the CNS, the locus of gut control is chiefly within the limbic system, a region of the mammalian brain responsible for both the internal and external homeostasis of the organism. The limbic system also plays a central role in emotionality, which is a nonverbal system that facilitates survival and threat avoidance, social interaction and learning. The generation of emotion and associated physiologic changes are the work of the limbic system and, from a neuroanatomic perspective, the ‘mind‐body interaction’ may largely arise in this region. Finally, the limbic system is also involved in the ‘top down’ modulation of visceral pain transmission as well as visceral perception. A better understanding of the interactions of the CNS, ENS and enteric immune system will significantly improve our understanding of ‘functional’ disorders and allow for a more pathophysiologic definition of categories of patients currently lumped under the broad umbrella of FGID.

title: Effects of aging on cholinergic neuromuscular transmission in isolated small intestine of ad libitum fed and calorically‐restricted rats
abstract: Age‐associated losses of enteric neurons have been described. In rat ileum, myenteric neurons lost during aging have been reported to be predominantly cholinergic, and caloric restriction (CR) has been shown to protect against these losses. Cholinergic myenteric neurons include excitatory motor neurons, so the aim of this work was to determine whether neuronal loss in ad libitum (AL)‐fed animals is reflected in dysfunctional cholinergic neuromuscular transmission, and if CR reduces any such dysfunction.

title: Oxidative Status and Lipofuscin Accumulation in Urothelial Cells of Bladder in Aging Mice
abstract: Age-related changes in various tissues have been associated with the onset of a number of age-related diseases, including inflammation and cancer. Bladder cancer, for instance, is a disease that mainly afflicts middle-aged or elderly people and is mostly of urothelial origin. Although research on age-related changes of long-lived post-mitotic cells such as neurons is rapidly progressing, nothing is known about age-related changes in the urothelium of the urinary bladder, despite all the evidence confirming the important role of oxidative stress in urinary bladder pathology. The purpose of this study was thus to investigate the oxidative status and age-related changes in urothelial cells of the urinary bladder of young (2 months) and aging (20 months) mice by means of various methods. Our results demonstrated that healthy young urothelium possesses a powerful antioxidant defence system that functions as a strong defence barrier against reactive species. In contrast, urothelial cells of aging bladder show significantly decreased total antioxidant capacity and significantly increased levels of lipid peroxides (MDA) and iNOS, markers of oxidative stress. Our study demonstrates for the first time that ultrastructural alterations in mitochondria and accumulation of lipofuscin, known to be one of the aging pigments, can clearly be found in superficial urothelial cells of the urinary bladder in aging mice. Since the presence of lipofuscin in the urothelium has not yet been reported, we applied various methods to confirm our finding. Our results reveal changes in the oxidative status and structural alterations to superficial urothelial cells similar to those of other long-lived post-mitotic cells.

title: Influence of aging on gastric emptying of liquids, small intestine transit, and fecal output in rats
abstract: The gastric emptying of a liquid meal, the small bowel transit, and the number of pellets and fecal output produced during a 24-h period, were studied in young (three months), adult (12 months) and old (24 months) male Wistar rats. The gastric emptying after 20 min of an intragastrically administered liquid meal containing phenol red and methylcellulose was significantly decreased in old rats. The small bowel transit after 15 and 30 min of the front of a charcoal and Arabic gum containing intragastrically administered meal was similar in the three age groups. The number of pellets and the mass of the feces produced during a 24-h period were significantly decreased with age, while the food intake was similar. The water content of the pellets was similar in the three age groups. These results show decreased gastric emptying of liquids and decreased stool mass in old rats, corresponding with the previously reported age-related changes in colonic smooth muscle contractility. Small intestinal transit was well maintained with age.

title: Mitochondrial alterations and apoptosis in smooth muscle from aged rats.
abstract: We studied changes in mitochondrial morphology and function in the smooth muscle of rat colon. Under confocal microscopy, tissues loaded with potentiometric dye displayed rapid and spontaneous depolarization. Cyclosporin A (CsA), inhibitor of the permeability transition pore (PTP), caused an increase in mitochondrial membrane potential (DeltaPsim) in tissues from adult young animals. In aged rats these changes were not observed. This suggests that physiological activation of PTP in aged rats is reduced. Electron microscopy showed alterations of the mitochondrial ultrastructure in tissues from aged rats involving a decreased definition of the cristae and fragmentation of the mitochondrial membranes. We also detected an increase in apoptotic cells in the smooth muscle from aged animals. Our results show that the aging process changes PTP activity, the ability to maintain DeltaPsim and mitochondrial morphology. It is suggested that these can be associated with mitochondrial damage and cell death.

title: Changes in calcium channel current densities in rat colonic smooth muscle cells during development and aging.
abstract: The age-related changes of Ca2+ channel currents were investigated in freshly isolated single smooth muscle cells from the circular layer of the distal colon from the rat using the whole cell voltage clamp technique. Under physiological conditions (Ca2+ concentration of 2.0 mM), the averaged total Ca2+ current density increased markedly from 1.25 pA/pF in the newborn rat to 6.46 pA/pF in the 60-day-old rat; it then gradually declined with aging. Two types of Ca2+ channel currents seemed to be present; one type possessed more negative threshold potentials (-70 to -60 mV) when the cells were held at -80 or -100 mV and inactivated quickly. The voltage for peak current was -20 to -10 mV, and the reversal potential was +60 to +70 mV. This current was highly sensitive to low concentrations of Ni2+ (30 microM) but was resistant to nifedipine, diltiazem, cadmium, and tetrodotoxin. In contrast, the other type of Ca2+ channel current possessed more positive threshold potential (-40 mV) and inactivated more slowly. The voltage for peak current was 0 mV, and the reversal potential was +60 to +70 mV. This current was insensitive to low concentrations of Ni2+ but highly sensitive to nifedipine, diltiazem, and cadmium. These results suggest that the fast inactivating (transient) current might be T-type Ca2+ current [ICa(T)], and such cells were ICa(T) positive cells; whereas the sustained Ca2+ current was L-type Ca2+ current [ICa(L)], and such cells were ICa(L) positive cells. Our results showed that the fraction of ICa(T) positive cells increased with development; the current densities of both ICa(L) and ICa(T) also increased with development.(ABSTRACT TRUNCATED AT 250 WORDS)

title: Aging-related changes of intracellular Ca2+ stores and contractile response of intestinal smooth muscle
abstract: In this study, we investigated the effect of aging on intracellular Ca2+ stores, as sarcoendoplasmic reticulum (SR) and mitochondria, and the influence of these compartments on contraction of rat colon smooth muscle [Bitar, K.N., 2003. Aging and neural control of the GI tract V. Aging and gastrointestinal smooth muscle: from signal transduction to contractile proteins. , G1-G7; Marijic, J., Li, Q.X., Song, M., Nishimaru, K., Stefani, E., Toro, L., 2001. Decreased expression of voltage-and Ca2+-activated K+ channels in coronary smooth muscle during aging.  Rubio, C., Moreno, A., Briones, A. Ivorra, M.D., D'Ocon, P., Vila, E., 2002. Alterations by age of calcium handling in rat resistance arteries. ), 832-840]. Calcium stores and contraction were evaluated by simultaneous measurements of fluorescence and tension in smooth muscle strips loaded with fura-2. Results showed that activation of muscarinic receptors by methylcholine (MCh, 10 microM), induced a greater contraction in aged rats than in adult animals. The inhibition of Ca2+ ATPase by thapsigargin (TG, 1 microM) did not prevent the refilling of SR either in adult or aged rats. MCh, in the presence of TG, induced an increase in transient fluorescence, indicating a release of Ca2+ from TG-insensitive compartment. The mitochondrial uncoupler, FCCP (5 microM), caused a greater increase in intracellular Ca2+ and tension in aged rats, indicating that mitochondria may accumulate more Ca2+ during aging. The present results show that changes in intracellular Ca2+ stores, such as mitochondria and SR, affect contraction and may cause dysfunctions during aging that could culminate in severe alterations of Ca2+ homeostasis and cell damage.

title: Ectopic expression of caveolin-1 restores physiological contractile response of aged colonic smooth muscle.
abstract: Reduced colonic motility has been observed in aged rats with a parallel reduction in acetylcholine (ACh)-induced myosin light chain (MLC(20)) phosphorylation. MLC(20) phosphorylation during smooth muscle contraction is maintained by a coordinated signal transduction cascade requiring both PKC-alpha and RhoA. Caveolae are membrane microdomains that permit rapid and efficient coordination of different signal transduction cascades leading to sustained smooth muscle contraction of the colon. Here, we show that normal physiological contraction can be reinstated in aged colonic smooth muscle cells (CSMCs) upon transfection with wild-type caveolin-1 through the activation of both the RhoA/Rho kinase and PKC pathways. Our data demonstrate that impaired contraction in aging is an outcome of altered membrane translocation of PKC-alpha and RhoA with a concomitant reduction in the association of these molecules with the caveolae-specific protein caveolin-1, resulting in a parallel decrease in the myosin phosphatase-targeting subunit (MYPT) and CPI-17 phosphorylation. Decreased MYPT and CPI-17 phosphorylation activates MLC phosphatase activity, resulting in MLC(20) dephosphorylation, which may be responsible for decreased colonic motility in aged rats. Importantly, transfection of CSMCs from aged rats with wild-type yellow fluorescent protein-caveolin-1 cDNA restored translocation of RhoA and PKC-alpha and phosphorylation of MYPT, CPI-17, and MLC(20), thereby restoring the contractile response to levels comparable with young adult rats. Thus, we propose that caveolin-1 gene transfer may represent a promising therapeutic treatment to correct the age-related decline in colonic smooth muscle motility.

title: Changes in interstitial cells of cajal with age in the human stomach and colon
abstract: Aging produces inevitable changes in the function of most organs including the gastrointestinal tract. Together with enteric nerves and smooth muscle cells, interstitial cells of Cajal (ICC) play a key role in the control of gastrointestinal motility, yet little is known about the effect of aging on ICC. The aim of this study was to determine the effect of aging on ICC number and volume in the human stomach and colon.

title: Innervation of the gastrointestinal tract: Patterns of aging
abstract: The gastrointestinal (GI) tract is innervated by intrinsic enteric neurons and by extrinsic projections, including sympathetic and parasympathetic efferents as well as visceral afferents, all of which are compromised by age to different degrees. In the present review, we summarize and illustrate key structural changes in the aging innervation of the gut, and suggest a provisional list of the general patterns of aging of the GI innervation. For example, age-related neuronal losses occur in both the myenteric plexus and submucosal plexus of the intestines. These losses start in adulthood, increase over the rest of the life span, and are specific to cholinergic neurons. Parallel losses of enteric glia also occur. The extent of neuronal and glial loss varies along an oral-to-anal gradient, with the more distal GI tract being more severely affected. Additionally, with aging, dystrophic axonal swellings and markedly dilated varicosities progressively accumulate in the sympathetic, vagal, dorsal root, and enteric nitrergic innervation of the gut. These dramatic and consistent patterns of neuropathy that characterize the aging autonomic nervous system of the GI tract are candidate mechanisms for some of the age-related declines in function evidenced in the elderly.

title: Aging and gastrointestinal neuromuscular function: insights from within and outside the gut
abstract: Understanding the effects of aging on the gut neuromuscular axis is of growing and profound importance in light of demographic data demonstrating a steady increase in the aged population globally. Likely areas of significant importance include the potential effects of aging on the extrinsic and intrinsic innervations, smooth muscle function in the human colon, and determination of whether specific biomarkers can be identified in the gut neural plexi, ICC, glial cells or smooth muscle that predict the onset of neurodegeneration. Age-related neuronal losses occur in both the myenteric plexus and submucosal plexus. In general, these losses start in adulthood and progress during the lifespan and involve cholinergic neurons predominately. Parallel age-dependent loss of enteric glia is also observed. The drop-out of these cell populations follows an oral-anal gradient, with greater losses noted distally. Dystrophic axonal swelling and dilated varicosities also increase in an age-dependent manner in the extrinsic innervations (vagal, DRG and sympathetic pathways), as well as, nitrergic neurons in the gut. 
 
Advanced age is associated with increased oxidative stress and mitochondrial dysfunction at the cellular level, culminating in disequilibrium between cytoprotective and cytotoxic pathways favoring the latter. Caloric restriction and/or diets supplemented with specific nutrients may help attenuate the effects of aging on neuromuscular function.

title: Cellular changes in the enteric nervous system during ageing.
abstract: The intrinsic neurons of the gut, enteric neurons, have an essential role in gastrointestinal functions. The enteric nervous system is plastic and continues to undergo changes throughout life, as the gut grows and responds to dietary and other environmental changes. Detailed analysis of changes in the ENS during ageing suggests that enteric neurons are more vulnerable to age-related degeneration and cell death than neurons in other parts of the nervous system, although there is considerable variation in the extent and time course of age-related enteric neuronal loss reported in different studies. Specific neuronal subpopulations, particularly cholinergic myenteric neurons, may be more vulnerable than others to age-associated loss or damage. Enteric degeneration and other age-related neuronal changes may contribute to gastrointestinal dysfunction that is common in the elderly population. Evidence suggests that caloric restriction protects against age-associated loss of enteric neurons, but recent advances in the understanding of the effects of the microbiota and the complex interactions between enteric ganglion cells, mucosal immune system and intestinal epithelium indicate that other factors may well influence ageing of enteric neurons. Much remains to be understood about the mechanisms of neuronal loss and damage in the gut, although there is evidence that reactive oxygen species, neurotrophic factor dysregulation and/or activation of a senescence associated phenotype may be involved. To date, there is no evidence for ongoing neurogenesis that might replace dying neurons in the ageing gut, although small local sites of neurogenesis would be difficult to detect. Finally, despite the considerable evidence for enteric neurodegeneration during ageing, and evidence for some physiological changes in animal models, the ageing gut appears to maintain its function remarkably well in animals that exhibit major neuronal loss, indicating that the ENS has considerable functional reserve.

title: Counting neurons is not as easy as ‘one‐two, three’
abstract: An accurate determination of the number of neurons in a segment of bowel is fundamental to establish population norms and identify neurodegenerative conditions, including age‐related loss of myenteric ganglion cells. Although the latter phenomenon has been observed by several laboratories in various mammals, in this issue of Neurogastroenterology and Motility, Gamage et al. present evidence that colonic myenteric ganglion cells are maintained in aged mice. These discordant findings prompt a thoughtful consideration, the range of variables affecting the accuracy of neuronal counts and the survival of neuronal populations in aging animals.

title: Reactive oxygen species, dietary restriction and neurotrophic factors in age‐related loss of myenteric neurons
abstract: We have studied the mechanisms underlying nonpathological age‐related neuronal cell death. Fifty per cent of neurons in the rat enteric nervous system are lost between 12 and 18 months of age in ad libitum (AL) fed rats. Caloric restriction (CR) protects almost entirely against this neuron loss. Using the ROS‐sensitive dyes, dihydrorhodamine (DHR) and 2‐[6‐(4′‐hydroxy)phenoxy‐3H‐xanthen‐3‐on‐9‐yl]benzoic acid (HPF) in vitro, we show that the onset of cell death is linked with elevated intraneuronal levels of reactive oxygen species (ROS). Treatment with the neurotrophic factors NT3 and GDNF enhances neuronal antioxidant defence in CR rats at 12–15 months and 24 months but not in adult or aged AL‐fed animals. To examine the link between elevated ROS and neuronal cell death, we assessed apoptotic cell death following in vitro treatment with the redox‐cycling drug, menadione. Menadione fails to increase apoptosis in 6‐month neurons. However, in 12–15mAL fed rats, when age‐related cell death begins, menadione induces a 7‐ to 15‐fold increase in the proportion of apoptotic neurons. CR protects age‐matched neurons against ROS‐induced apoptosis. Treatment with neurotrophic factors, in particular GDNF, rescues neurons from menadione‐induced cell death, but only in 12–15mCR animals. We hypothesize that CR enhances antioxidant defence through neurotrophic factor signalling, thereby reducing age‐related increases in neuronal ROS levels and in ROS‐induced cell death.

title: A senescent cell bystander effect: senescence-induced senescence
abstract: Senescent cells produce and secrete various bioactive molecules including interleukins, growth factors, matrix‐degrading enzymes and reactive oxygen species (ROS). Thus, it has been proposed that senescent cells can damage their local environment, and a stimulatory effect on tumour cell growth and invasiveness has been documented. However, it was unknown what effect, if any, senescent cells have on their normal, proliferation‐competent counterparts. We show here that senescent cells induce a DNA damage response, characteristic for senescence, in neighbouring cells via gap junction‐mediated cell–cell contact and processes involving ROS. Continuous exposure to senescent cells induced cell senescence in intact bystander fibroblasts. Hepatocytes bearing senescence markers clustered together in mice livers. Thus, senescent cells can induce a bystander effect, spreading senescence towards their neighbours in vitro and, possibly, in vivo.

title: Alpha-synuclein immunopositive aggregates in the myenteric plexus of the aging Fischer 344 rat
abstract: Dystrophic axons and terminals are common in the myenteric plexus and smooth muscle of the gastrointestinal (GI) tract of aged rats. In young adult rats, alpha-synuclein in its normal state is abundant throughout the myenteric plexus, making this protein-which is prone to fibrillization-a candidate marker for axonopathies in the aged rat. To determine if aggregation of alpha-synuclein is involved in the formation of age-related enteric neuropathies, we sampled the stomach, small intestine and large intestine of adult, middle-aged, and aged virgin male Fischer 344 rats stained for alpha-synuclein in both its normal and pathological states. Alpha-synuclein-positive dystrophic axons and terminals were present throughout the GI tract of middle-aged and aged rats, with immunohistochemical double labeling demonstrating co-localization within nitric oxide synthase-, calretinin-, calbindin-, or tyrosine hydroxylase-positive markedly swollen neurites. However, other dystrophic neurites positive for each of these four markers were not co-reactive for alpha-synuclein. Similarly, a subpopulation of alpha-synuclein inclusions contained deposits immunostained with an anti-tau phospho-specific Ser(262) antibody, but not all of these hyperphosphorylated tau-positive aggregates were co-localized with alpha-synuclein. The presence of heteroplastic and potentially degenerating neural elements and protein aggregates both positive and negative for alpha-synuclein suggests a complex chronological relationship between the onset of degenerative changes and the accumulation of misfolded proteins. Additionally, proteins other than alpha-synuclein appear to be involved in age-related axonopathies. Finally, this study establishes the utility of the aging Fischer 344 rat for the study of synucleopathies and tauopathies in the GI tract.

title: As the gut ages: Timetables for aging of innervation vary by organ in the Fischer 344 rat
abstract: To explore the effects of aging on the vagal innervation of the gastrointestinal (GI) tract, male Fischer 344 rats at 3 and 24 months of age were injected in the left nodose ganglion with 3 μl of either 4% wheat germ agglutinin‐horseradish peroxidase (to label sensory endings) or 1% cholera toxin subunit B‐horseradish peroxidase (to label motor endings). The stomach and duodenum were prepared as wholemounts and processed with tetramethyl benzidine. In addition, to study age‐related changes in the myenteric plexus, the stomachs, small intestines, and large intestines from 3‐, 12‐, 21‐, 24‐ and 27‐month‐old rats were prepared as wholemounts and processed with Cuprolinic Blue (to stain the neurons). Vagal afferent endings, motor terminal profiles, and myenteric neurons were counted and mapped with a sampling grid. In the stomach, both the vagal and myenteric innervation were stable between the ages of 3 and 24 months; however, a decrease in the number of myenteric neurons in the forestomach was noted at 27 months. In the small and large intestines, myenteric cell loss occurred by 12 months of age, progressed with age, and appeared to be governed by several general principles: (1) the rate of cell loss was organ‐specific, with a gradient of increasing severity from proximal to distal in the gut; (2) within organs of the GI tract, the rate of cell loss differed between regions; and (3) for given regions, cell losses progressed linearly with increasing age. The findings suggest that a positive relationship exists between the density of vagal extrinsic innervation and myenteric neuron survival; however, whether this results from the vagal innervation and/or other factor(s) protecting or rescuing myenteric neurons from age‐related attrition remains to be determined.  2001.

title: A quantitative study of the effects of age on the noradrenergic innervation of Auerbach's plexus in the rat
abstract: Noradrenergic nerves were demonstrated in stretch preparations of Auerbach's plexus and longitudinal muscle from the proximal jejunum of Wistar rats using glyoxylic acid-induced fluorescence. The density of the noradrenergic nerve plexus and the number of nerve terminal varicosities/frame area were assessed using a Quantimet 800 image analyser and the number of varicosities/unit length of nerve was measured manually with a calibrated planimeter. With increasing age, especially between 12 and 18 months there occurs a breakdown of plexus regularity and noticeably reduced levels of axonal fluorescence. Image analysis showed a decrease in the total area of the plexus of more than 50% and a decrease of almost 75% in the total number of varicosities. The frequency of varicosities per 100 micron of axon decreased from 18.79 at 12 months to 14.79 at 18 months. Significant changes in these parameters did not occur during the following 6 months. The dramatic decrease in the density of the noradrenergic innervation of Auerbach's plexus and the fall in number of varicosities with age implies a reduction in the potential of the sympathetic nervous system to influence control over motility of the jejunum in the aged rat.

title: Sympathetic axonopathies and hyperinnervation in the small intestine smooth muscle of aged Fischer 344 rats
abstract: It is well documented that the intrinsic enteric nervous system of the gastrointestinal (GI) tract sustains neuronal losses and reorganizes as it ages. In contrast, age-related remodeling of the extrinsic sympathetic projections to the wall of the gut is poorly characterized. The present experiment, therefore, surveyed the sympathetic projections to the aged small intestine for axonopathies. Furthermore, the experiment evaluated the specific prediction that catecholaminergic inputs undergo hyperplastic changes. Jejunal tissue was collected from 3-, 8-, 16-, and 24-month-old male Fischer 344 rats, prepared as whole mounts consisting of the muscularis, and processed immunohistochemically for tyrosine hydroxylase, the enzymatic marker for norepinephrine, and either the protein CD163 or the protein MHCII, both phenotypical markers for macrophages. Four distinctive sympathetic axonopathy profiles occurred in the small intestine of the aged rat: (1) swollen and dystrophic terminals, (2) tangled axons, (3) discrete hyperinnervated loci in the smooth muscle wall, including at the bases of Peyer's patches, and (4) ectopic hyperplastic or hyperinnervating axons in the serosa/subserosal layers. In many cases, the axonopathies occurred at localized and limited foci, involving only a few axon terminals, in a pattern consistent with incidences of focal ischemic, vascular, or traumatic insult. The present observations underscore the complexity of the processes of aging on the neural circuitry of the gut, with age-related GI functional impairments likely reflecting a constellation of adjustments that range from selective neuronal losses, through accumulation of cellular debris, to hyperplasias and hyperinnervation of sympathetic inputs.

title: Aging and neural control of the GI tract. II. Neural control of the aging gut: can an old dog learn new tricks?
abstract: There has been a dramatic increase in funding available for aging research, primarily due to the fact that answers to questions on aging are likely to have a major impact on the well-being and healthy aging of the world's population for decades to come. The incidence of certain gastrointestinal problems, such as dysphagia and constipation, increases dramatically with age. Changes in gastrointestinal neuromuscular function with aging have been demonstrated in both human and animal models of aging. This article focuses on recent advances in our knowledge of the effects of aging on gastrointestinal function, treatment options, and future opportunities for research.

title: Fat deposition in the tunica muscularis and decrease of interstitial cells of Cajal and nNOS-positive neuronal cells in the aged rat colon.
abstract: Little is known about the time course of aging on interstitial cells of Cajal (ICC) of colon. The aim of this study was to investigate the change of morphology, ICC, and neuronal nitric oxide synthase (nNOS)-immunoreactive cells in the aged rat. The proximal colon of 344 Fischer rats at four different ages (6, 31, 74 wk, and 2 yr) were studied. The immunoreactivity of c-Kit, nNOS, anti-protein gene product 9.5, and synaptophysin were counted after immunohistochemistry. The c-kit, stem cell factor (ligand of Kit), and nNOS mRNA were measured by real-time PCR. c-Kit and nNOS protein were assessed by Western blot. Isovolumetric contractile force measurement and electrical field stimulation (EFS) were conducted. The area of intramuscular fat deposition significantly increased with age after 31 wk. c-Kit-immunoreactive ICC and nNOS-immunoreactive neurons and nerve fibers significantly declined with age. mRNA and protein expression of c-kit and nNOS decreased with aging. The functional study showed that the spontaneous contractility was decreased in aged rat, whereas EFS responses in the presence of atropine and L-NG-Nitroarginine methyl ester were increased in aged rat. In conclusion, the decrease of proportion of proper smooth muscle, the density of ICC and nNOS-immunoreactive neuronal fibers, and the number of nNOS-immunoreactive neurons during the aging process may explain the aging-associated colonic dysmotility.

title: Immunohistochemical characterisation of sympathetic and parasympathetic pelvic neurons projecting to the distal colon in the male rat
abstract: The pelvic ganglia are mixed ganglia containing both sympathetic and parasympathetic neurons that receive spinal input via the hypogastric (lumbar cord) and pelvic nerves (sacral cord), respectively. A recent study has utilised immunohistochemistry against synaptophysin (a protein associated with small vesicles) to visualise the preganglionic terminals in these ganglia. By selectively cutting the hypogastric or pelvic nerves and allowing subsequent terminal degeneration, the populations of parasympathetic and sympathetic preganglionic terminals, respectively, can be visualised. The present study has used this method in conjunction with retrograde labelling of pelvic neurons from the distal colon and double label immunofluorescence against tyrosine hydroxylase and vasoactive intestinal polypeptide (VIP) to identify and characterise the sympathetic and parasympathetic neurons projecting to the distal colon from the major pelvic ganglia of the male rat. Approximately equal numbers of distal colonic-projecting pelvic neurons are sympathetic and parasympathetic. Almost all noradrenergic neurons are sympathetic. Of the VIP neurons that project to the distal colon approximately one third are sympathetic, one third parasympathetic and the remaining third are possibly innervated by both the lumbar and sacral cord. Extrapolation from our results also suggests that the majority of non-noradrenergic neuropeptide Y neurons (which are known to comprise the remainder of the neurons) are parasympathetic. These studies have demonstrated that the pelvic ganglia are a major source of sympathetic innervation to the distal bowel and have further shown that the distal colon is another target for the non-noradrenergic sympathetic neurons of the pelvic ganglia.

title: The effect of ageing on the histochemically demonstrable catecholamines in the hypogastric (main pelvic) ganglion of the rat
abstract: SummaryThe effect of ageing on adrenergic neurons was studied in the hypogastric ganglion of the male rat using the formaldehyde-induced fluorescence method.With age, two changes were obvious. Firstly, the fluorescence intensity of the neurons decreased throughout postnatal life and the number of completely non-fluorescent adrenergic neurons increased. Secondly, the amount of non-specific fluorescence due to lipofuscin pigment increased. The pigment fluorescence was also found around the neurons in satellite cells.

title: Effects of senescence and citral on neuronal vacuolar degeneration in rat pelvic ganglia.
abstract: A significant part of the morbidity in elderly men involves pelvic organs and their autonomic neural regulation. Environmental stimuli also impair the structure and function of pelvic organs. One of these factors is citral, a widely-used cosmetic fragrance constituent, which causes severe prostatic hyperplasia in rats. In this study, we assessed the effect of topical administration of citral (30 days) on the morphology of pelvic ganglia (PG) in young adult and old Wistar rats. Neuronal vacuolar degeneration with preserved nuclei of PG neurons was observed in untreated senescent, but not young rats. Citral significantly increased the rate of vacuolated neurons in old rats (from 3 to 14%), but only slightly in young ones (from 0 to 0.5-0.3%). Similar lesions were not found in inferior cervical or celiac ganglia, in either group. This shows that environmental stimuli enhance age-related processes of vacuolar neuronal degeneration in PG, and may contribute to the dysfunction of pelvic organs in the elderly.

title: Localisation of NADPH-diaphorase and acetylcholinesterase activities and of tyrosine hydroxylase and neuropeptide-Y immunoreactivity in neurons of the hypogastric ganglion of young adult and aged rats.
abstract: Neurons in the hypogastric (main pelvic) ganglia of 4- and 24-month-old male rats were investigated by enzyme histochemical methods for NADPH-diaphorase (NADPH-d) and acetylcholinesterase (AChE) activities and by immunofluorescence for tyrosine hydroxylase (TH) and neuropeptide Y (NPY) immunoreactivities. Systematic random sampling of standard sized areas of ganglion parenchyma revealed a content (per unit area) of 40.9 +/- 8.41 NADPH-d-positive neurons and 14.42 +/- 6.7 intensely AChE-positive neurons. In the aged rats the staining intensity was unchanged, but reductions in the numbers of cells stained for NADPH-d and AChE were not significantly different. Similar counts of TH- and NPY-immunoreactive neurons revealed values of 23.2 +/- 1.77 and 19.94 +/- 4.9, respectively, suggesting frequent co-localisation. The numbers of TH- and NPY-immunoreactive neurons were found to have decreased with age by 53% and 60%, respectively. Staining of consecutive sections revealed that those neurons which stained positively for NADPH-d did not show immunoreactivity for TH or NPY, and those neurons that were immunoreactive for TH or NPY did not contain intense NADPH-d staining. Occasional NPY-1R neurons were both TH- and NADPH-d-negative. These results suggest that NADPH-d staining is predominantly confined to the parasympathetic neuron population of the hypogastric ganglion and that it is the sympathetic neuron population alone that decreases in number with age.

title: Decrease in synapsin I staining in the hypogastric ganglion of aged rats
abstract: The rat hypogastric ganglion (HG) contains populations of both sympathetic and parasympathetic postganglionic neurons which supply the lower pelvic viscera. These neuron populations can be identified by tyrosine hydroxylase (TH) and NADPH-diaphorase (NADPH-d) staining, respectively. The effects of age on the distribution of synapsin I, a nerve terminal marker, in relation to these neuron populations has been investigated in young adult and aged rats. Most synapsin staining was axosomatic and was markedly reduced in the aged animals particularly in relation to sympathetic (NADPH-d-negative/TH-positive) neurons. Image analysis of synapsin I staining in relation to individual sympathetic neurons confirmed that there was a reduction with age of about 50% but no change in synapsin I staining in relation to parasympathetic neurons. These results suggest that synaptic transmission and peripheral integration may be affected in old age and that the autonomic control of the pelvic viscera may be compromised as a result, particularly with regard to the sympathetic innervation. Other autonomic ganglia were also studied for comparison but no such age-related differences were observed.

title: Decreased calbindin-D28k immunoreactivity in aged rat sympathetic pelvic ganglionic neurons
abstract: The rat major pelvic ganglion contains the majority of sympathetic and parasympathetic postganglionic neurons that innervate the pelvic viscera. Previous studies have indicated that it is only the sympathetic population of this ganglion that is susceptible to age-associated changes. We have examined the distribution of the neuronal calcium binding proteins calbindin-D28k, calretinin and parvalbumin by immunohistochemistry in young adult and aged rats and have discovered that calbindin-D28k is only present in the sympathetic neurons (identified by tyrosine hydroxylase immunostaining) and not in parasympathetic neurons (identified by VIP immunostaining). In the aged rats the number of calbindin-immunoreactive sympathetic neurons of the major pelvic ganglion was dramatically reduced. Calretinin and parvalbumin-immunoreactivity was present at a lower level of fluorescence than that of calbindin immunoreactivity in all the neurons of the major pelvic ganglion and this level was unchanged in aged rats. Thus we suggest that the decline of intracellular calbindin D28k levels may lead to impaired calcium buffering capacity which might be a contributory factor in the age-associated attrition of pelvic sympathetic neurons.

title: Age-related changes in the morphology of preganglionic neurons projecting to the rat hypogastric ganglion
abstract: SummaryThe aim of this study was to investigate age-related changes in preganglionic neurons of the lumbar and sacral spinal cord of the male rat that may underlie impaired control of the urogenital system in old age. Preganglionic sympathetic and parasympathetic neurons of 4- and 24-month-old rats were identified by retrograde axonal tracing with cholera toxin subunit-B followed by immunocytochemistry. Labelled preganglionic neurons were scanned on the confocal microscope. Measurements were made of soma area, number of primary dendrites, number of dendritic branch points and total dendritic length. there were significant decreases in the number of dendritic branch points and total dendritic length of sympathetic preganglionic neurons in the aged rats compared to the adult group. The soma area and number of primary dendrites were not significantly different. Some cells exhibited signs of degeneration, such as swelling of the soma and distension of the proximal part of primary dendrites. No significant differences were found in any of the parameters measured for the parasympathetic neurons. The changes in dendritic morphology of sympathetic preganglionic neurons may reflect altered central and peripheral control of pelvic viscera in old age.

title: Age-related changes in the morphology of preganglionic neurons projecting to the paracervical ganglion of nulliparous and multiparous rats
abstract: The aim of this study was to investigate age-related changes in preganglionic neurons in the lumbar and sacral spinal cord of the female rat that may underlie impaired control of the urogenital system in old age. Preganglionic sympathetic and parasympathetic neurons of young adult, aged nulliparous and aged multiparous rats were identified by retrograde tracing with cholera toxin subunit-B and subsequent immunocytochemistry. Labeled preganglionic neurons were scanned, processed and analyzed using the confocal microscope. Measurements were made of soma area, number of primary dendrites, number of dendritic branch points and total dendritic length. There were significant decreases in the number of primary dendrites, number of dendritic branch points and total dendritic length of sympathetic preganglionic neurons in both nulliparous and multiparous aged rats compared to the young adult group. No significant differences were found in the dendritic morphology of aged parasympathetic preganglionic neurons. Soma area was not significantly different between age groups for sympathetic or parasympathetic preganglionic neurons. These changes in dendritic morphology may result in altered control of the lower urogenital tract in aged nulliparous and multiparous female rats.

title: The effects of ageing on the distribution of vesicular acetylcholine transporter immunoreactive inputs to pelvic motoneurons of male Wistar rats
abstract: Age-related changes in the number and size of large cholinergic terminals immunoreactive for vesicular acetylcholine transporter (VAChT), were documented for the dorsolateral nucleus (DLN), retrodorsolateral nucleus (RDLN) and spinal nucleus of the bulbospongiosus (SNB) of the lumbosacral spinal cord of male rats. The most significant changes were a large increase in the number and size of cholinergic terminals within the DLN of aged animals, together with a small decrease in terminal number within the RDLN. No significant age-associated differences in VAChT labeling were seen within the SNB. In both age groups, SNB motoneurons projecting to the levator ani muscle received about 9 to 10 contacts from large cholinergic terminals. Ultrastructural examination of the terminals revealed structures likely to be postsynaptic subsurface cisterns that are characteristic of type C terminal boutons. Since both the DLN and SNB contain motoneurons innervating pelvic muscles and sphincters, these findings provide further evidence for a central cholinergic influence on micturition and sexual reflexes and suggest that this may remain robust in the face of ageing.

title: The serotoninergic bulbospinal system and brainstern‐spinal cord content of serotonin‐, TRH‐, and substance P‐like immunoreactivity in the aged rat with special reference to the spinal cord motor nucleus
abstract: The 5‐hydroxytryptamine (5HT) containing bulbospinal pathway was studied with immunohistochemical (IF) and chemical techniques in 2–3 and 30 months old male Sprague‐Dawley rats. The coexisting neuropeptides substance P (SP), thyrotropin‐releasing hormone (TRH) and galanin were also analysed. Furthermore, the expression of mRNA encoding aromatic L‐amino acid decarboxylase (AADC), prepro‐TRH, and preprotachykinin (prepro‐SP) was analysed with in situ hybridization (ISH) in the midline raphé nuclei in the lower brainstem.