bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of Angiotensin II and the AT1 Receptor Antagonist Losartan on the Renal Excretion of Urodilatin
Authors: Heringlake M. , Bahlmann L. , Klaus S. , Wagner K. , Schmucker P. , Pagel H.
Published: April 2003

Background: The precise mechanisms regulating the natriuretic peptide urodilatin (ANP-95-126) remain to be defined. Renal excretion of urodilatin (UUROV) has been shown to be modified by variations in plasma sodium and renal perfusion pressure. This suggests a relationship between urodilatin and the renin-angiotensin system. Methods: We investigated the effects of angiotensin II (AII, 0.1 nmol/l) and the AT1 receptor antagonist losartan (LS, 1 µmol/l) on UUROV and renal function in isolated rat kidneys perfused for 180 min in a closed circuit system. A further series employing a vasoconstricting concentration of endothelin-1 (ET-1, 0.01 nmol/l) was performed to explore the effects of vasoconstriction and glomerular filtration rate (GFR) on UUROV. Results: Urine flow (UV) and urinary sodium excretion (UNaV) decreased and renal vascular resistance (RVR) increased after treatment with AII (n = 5) in comparison with a control group (n = 6; p < 0.05). Treatment with LS (n = 5) and AII+LS (n = 5) had no significant effect on these parameters. GFR decreased after AII (p < 0.05) and was not significantly altered by other interventions. UUROV decreased after AII (p < 0.05) and was comparable to the control group after LS and AII+LS. ET-1 (n = 5) induced a significant increase in RVR and decreased UV and UNaV (p < 0.05). Point-to-point analysis revealed that the ET-1-induced vasoconstriction and the subsequent decrease in GFR had no effect on UUROV. Conclusions: This suggests that vasoconstrictory concentrations of AII decrease UUROV in the isolated perfused rat kidney. The lack of effect of ET-1 on UUROV suggests that the AII-induced alterations in urodilatin excretion cannot be explained by vasoconstriction per se.
High Glucose Levels Alter Angiotensin II-Induced Ca2+ Uptake via PKC and cAMP Pathways in Renal Proximal Tubular Cells
Authors: Park Soo Hyun , Shin Sung Shik , Han Ho Jae
Published: April 2003

Although a dysfunction of the calcium metabolism occurs in diabetes mellitus, alterations of Ca2+ uptake induced by angiotensin II (ANG II) in renal proximal tubular cells (PTCs) grown in high-glucose medium are not fully elucidated. Thus, we examined whether high glucose concentrations can induce an alteration of the ANG II effect on the Ca2+ uptake and its action mechanism in primary cultured renal PTCs. PTCs were exposed to different glucose concentrations (5–100 mM) and time intervals (0–48 h). There was a sustained increase of Ca2+ uptake at glucose concentrations >15 mM. Thus, we selected 25 mM glucose and incubation for 48 h to maintain a hyperglycemic condition in vitro, unlike short-time regulatin. ANG II significantly inhibited the Ca2+ uptake in a dose-dependent manner in a 5-mM glucose medium. In addition, downregulation of ANG II receptors appeared in a glucose dose dependent manner. However, PTCs treated with 25 mM glucose for 48 h, not 12 h, did not exhibit the inhibitory effect of ANG II (10–7 M) on Ca2+ uptake, although the inhibitory effect of ANG II on Ca2+ uptake occurred in the presence of 25 mM mannitol or L-glucose. Staurosporine, bisindolylmaleimide I (protein kinase C, PKC, inhibitors), 12-o-tetradecanoylphorbol 13-acetate pretreatment, SQ 22536 (an adenylate cyclase inhibitor), and myristoylated protein kinase A inhibitor amide 14–22 (a protein kinase A inhibitor) blocked the 25-mM-glucose-induced alteration of ANG II effect on Ca2+ uptake. These results suggest that both PKC and cyclic adenosine monophosphate (cAMP) pathways are involved in the high-glucose-induced alteration of ANG II effect on Ca2+ uptake. Indeed, 25 mM glucose increased PKC activity and cAMP contents. In conclusion, a high glucose concentration altered ANG II induced inhibition of Ca2+ uptake via PKC and cAMP pathways in the PTCs.
Oxidative Stress and Renal Dysfunction in Salt-Sensitive Hypertension
Authors: Trolliet María R. , Rudd M. Audrey , Loscalzo Joseph
Published: April 2003

Hypertension is a risk factor for the development of end-stage renal disease. The mechanisms underlying hypertensive nephropathy are poorly understood. There is evidence, however, that in hypertension there is an accumulation of partially reduced oxygen and its derivatives, known collectively as reactive oxygen species, which may contribute to progressive renal dysfunction. In the present study, we assess the contribution of oxidative stress in the development of salt-dependent hypertensive nephrosclerosis. Going beyond previous end point studies, which inferred renal function either indirectly or only qualitatively, we have determined oxidative stress concurrently with direct and quantitative measurements of renal function (via inulin and p-aminohippuric acid clearances). Moreover, in this time-dependent study, the measurements have been taken under low- as well as high-salt diets. As was expected from previous studies, in the Dahl salt-sensitive rat, a high-salt diet (8% NaCl) resulted in the development of hypertension, in a decreased glomerular filtration rate, and in a decreased renal plasma flow as compared with the normotensive control, the Dahl salt-resistant rat. In addition, however, we found clear evidence for the accumulation of reactive oxygen species in renal tissue homogenates of Dahl salt-sensitive rats on the high-salt diet. Our time-dependent protocol also indicated that renal oxidative stress follows, in time, the development of hypertension. We also found that after 2 weeks of increased salt loading, Dahl salt-sensitive rats excreted less cyclic guanosine monophosphate and NOx than Dahl salt-resistant rats on the same diet. It is known that urinary cyclic guanosine monophosphate and NOx represent the activity and stable derivatives of renal NO·, respectively, and that they closely correlate with renal vascular resistance. Therefore, our results suggest that, in the Dahl salt-sensitive rat, increased oxidative stress is associated with salt-dependent hypertensive nephrosclerosis and that decreased NO· bioavailability may represent a common factor responsible for the vascular and glomerular dysfunction.
Expression of Oligodendrocyte-Specific Protein/Claudin-11 in the Human Fetal Forebrain
Authors: Ulfig Norbert , Briese Michael , Bohl Jürgen
Published: April 2003

Oligodendrocyte-specific protein (OSP)/claudin-11, which is the third most abundant CNS myelin protein, is localized to a variant of tight junctions in myelin sheaths. The distribution of this protein was investigated immunohistochemically in 7 human fetal brains (from 24 to 32 weeks of gestation. At 24 weeks of gestation, OSP/claudin-11-immunoreactive (IR) cell bodies are observed in the ganglionic eminence, internal capsule, medial medullary lamina and subthalamic nucleus. Between 30 and 32 weeks of gestation, cellular and fibrous immunolabeling is found in the above-mentioned brain areas. In addition, IR cell bodies are seen in the dorsal thalamus, globus pallidus and striatum. The distribution pattern of OSP/claudin-11-IR structures reflects which regions of the forebrain first display myelin sheaths. In addition, OSP/claudin-11 is expressed in the ganglionic eminence and adjacent cell clusters, indicating a role of this protein in the proliferation and migration of oligodendrocytes. Moreover, it is obvious that OSP/claudin-11 is first restricted to the somata of oligodendrocytes and later accumulates within their processes. This accumulation is in accordance with data in the literature demonstrating that OSP/claudin-11 is a specific protein of myelinic tight junctions. The latter may form a barrier isolating the extracellular compartment between myelin sheaths.
Periventricular Leukomalacia: The Role of Inflammatory Mediators and Microglia in Pathogenesis
Authors: Rezaie Payam , Dean Andrew
Published: April 2003

Periventricular leukomalacia (PVL) in the pre-term infant and in the newborn represents a major precursor of neurological dysfunction and intellectual impairment in later life. Neuropathological examination of cases with PVL reveals lesions which specifically involve periventricular areas of the deep white matter and comprise necrotic foci, selective loss of oligodendrocyte progenitor cells (OPCs), delayed myelination and axonal swelling accompanied by glial activation. The principal factors leading to white matter damage in PVL are centered around the intrinsic vulnerability of OPCs, which are susceptible to free radical-mediated damage and excitotoxicity induced by hypoxic ischaemia, cerebral hypoperfusion, as well as secondary associated events involving microglial and astrocytic activation and the release of pro-inflammatory cytokines such as tumour necrosis factor-α and interleukin-6. Additionally, intrauterine infection (chorioamnionitis) has also been proposed as a causative factor of PVL. Recent investigations have shown that inflammatory responses in the fetus and neonate can contribute towards neonatal brain injury and developmentally related disabilities. This article will discuss the potential contribution of inflammatory mediators and the resident immune cells of the nervous system, the microglia, to the pathological progression of PVL. These findings provide the basis for therapeutic strategies aimed at protecting the premature brain against inflammatory damage, which may prove beneficial for the treatment of PVL.
Methylene Blue Inhibits the Increase of Inducible Nitric Oxide Synthase Activity Induced by Stress and Lipopolysaccharide in the Medial Basal Hypothalamus of Rats
Authors: Lomniczi Alejandro , Cebral Elisa , Canteros Griselda , McCann Samuel M. , Rettori Valeria
Published: April 2003

In infection bacterial products such as lipopolysaccharides (LPS) induce inducible nitric oxide synthase (iNOS) that produces large quantities of NO toxic to the invading organisms, but also often has toxic effects on host cells. Therefore, inhibition of iNOS activity might be beneficial in combatting these adverse effects. To determine if methylene blue (MB), an oxidizing agent that inactivates iNOS, would reduce the iNOS levels in the medial basal hypothalami (MBH) of conscious male rats, LPS (5 mg/kg) was injected intravenously (i.v.), and after 3 h they were injected i.v. with either MB (3 mg/kg) or saline and the effects on iNOS in the MBH determined. iNOS was measured by conversion of labeled arginine into citrulline by incubating MBH in the absence of calcium (Ca2+) since iNOS does not require Ca2+ for activation. The results indicate that iNOS was induced by the injection of saline, but the induction by LPS was much greater, an increase of 10-fold above that of control sham-operated animals. Both the induction of iNOS from the stress of saline injections and LPS were completely eliminated by MB indicating that MB might be beneficial in preventing injury to brain tissue following LPS injection. There was no effect of either LPS or MB on the Ca2+-dependent constitutive NOS activity.
Effects of Pulsed High-Frequency Electromagnetic Fields on the Neuroendocrine System
Authors: Mann Klaus , Wagner Peter , Brunn Georg , Hassan Feisal , Hiemke Christoph , Röschke Joachim
Published: April 2003

The influence of pulsed high-frequency electromagnetic fields emitted from a circularly polarized antenna on the neuroendocrine system in healthy humans was investigated (900 MHz electromagnetic field, pulsed with 217 Hz, average power density 0.02 mW/cm2). Nocturnal hormone profiles of growth hormone (GH), cortisol, luteinizing hormone (LH) and melatonin were determined under polysomnographic control. An alteration in the hypothalamo-pituitary-adrenal axis activity was found with a slight, transient elevation in the cortisol serum level immediately after onset of field exposure which persisted for 1 h. For GH, LH and melatonin, no significant effects were found under exposure to the field compared to the placebo condition, regarding both total hormone production during the entire night and dynamic characteristics of the secretion pattern. Also the evaluation of the sleep EEG data revealed no significant alterations under field exposure, although there was a trend to an REM suppressive effect. The results indicate that weak high-frequency electromagnetic fields have no effects on nocturnal hormone secretion except for a slight elevation in cortisol production which is transient, pointing to an adaptation of the organism to the stimulus.
Effect of Melatonin on 24-Hour Rhythms of Ornithine Decarboxylase Activity and Norepinephrine and Acetylcholine Synthesis in Submaxillary Lymph Nodes and Spleen of Young and Aged Rats
Authors: Cardinali Daniel P. , Brusco Luis I. , GarcíaBonacho Manuel , Esquifino Ana I.
Published: April 2003

Young (50 days old) and old (18 months old) Sprague-Dawley rats were injected with mycobacterial Freund’s adjuvant to produce an inflammatory disease of the joints and were studied the day before, and on days 6, 12 and 18 after injection. At every postinjection interval examined, old rats had significantly lower circadian amplitudes of pineal melatonin content. On day 18 of arthritis development, decreased levels of pineal melatonin were also seen in young rats. A second study, carried out 18 days after the injection of Freund’s complete adjuvant and after 17 daily injections of 10 or 100 µg of melatonin in the evening, indicated that melatonin treatment restored the inflammatory response in old rats (assessed plethysmographically in hind paws) to the level found in young animals. In young rats, an inflammation-promoting effect of 100 µg melatonin could be demonstrated. As a consequence of the immune reaction, submaxillary lymph node and splenic ornithine decarboxylase activity (an index of lymph cell proliferation) augmented significantly, with acrophases of 24-hour rhythms in the afternoon for lymph nodes or in the morning for spleen. Mesor and amplitude of ornithine decarboxylase rhythm were lowest in old rats, while melatonin injection generally augmented its amplitude. Lymph node and splenic tyrosine hydroxylase activity (a presynaptic adrenergic marker) reached maximal values during early night hours while maximal values of [3H]acetylcholine synthesis (a presynaptic cholinergic marker) occurred during the afternoon in lymph nodes. Amplitude and mesor of these rhythms were lowest in old rats, an effect generally counteracted by melatonin treatment. The results suggest that inflammation is accompanied by an age-dependent, significant depression of pineal melatonin synthesis during adjuvant-induced arthritis and a decreased amplitude of the circadian rhythm of immune cell proliferation and autonomic activity in lymph nodes and spleen. These effects are counteracted by injection of melatonin, mainly in old rats.
Binding of the Non-Peptide Vasopressin V1a Receptor Antagonist SR-49059 in the Rat Brain: An in vitro and in vivo Autoradiographic Study
Authors: Tribollet Eliane , Raufaste Danielle , Maffrand Jean-Pierre , Serradeil-Le Gal Claudine
Published: April 2003

A potent non-peptide vasopressin (AVP) antagonist, SR-49059, displaying high stability and selective affinity for the V1a AVP receptor subtype, has recently been described. The objective of this study was to assess the binding properties and the penetrability of this compound in the rat brain. Both in vitro and in vivo binding autoradiography experiments were performed. In all studies, the liver was used as a reference V1a tissue. In vitro labelling of rat brain sections with [3H]SR-49059 was similar to that previously detected with [3H]AVP, which confirms that the majority of central AVP binding sites are V1a sites similar to peripheral V1a receptors. As expected, intense specific labelling occurred mainly in the lateral septum, the fundus striatum, the hypothalamic stigmoid nucleus and the area postrema-nucleus of the solitary tract complex. In vivo binding autoradiography showed that [3H]SR-49059 injected intravenously did not enter the brain parenchyma. Specific labelling was however clearly detectable in brain regions with permeable hematoencephalic barrier, the choroid plexus and other circumventricular organs expressing V1a receptors, namely the subfornical organ, the pineal gland and the area postrema. The specificity of [3H]SR-49059 binding in the latter structures was confirmed by the fact that labelling was prevented by pretreatment of animals with high doses of nonradioactive SR-49059. In conclusion, our study shows that [3H]SR-49059 is a suitable probe to investigate V1a receptors in the rat brain. We also demonstrate that although this compound is not able to enter the brain tissue from the peripheral circulation, it does bind specifically to regions devoid of blood-brain barrier and known to be involved in autonomic regulations.
Serotonin in Golden Hamster Testes: Testicular Levels, Immunolocalization and Role during Sexual Development and Photoperiodic Regression-Recrudescence Transition
Authors: Frungieri MónicaB. , Gonzalez-Calvar SilviaI. , Rubio Modesto , Ozu Marcelo , Lustig Livia , Calandra RicardoS.
Published: April 2003

Serotonin (5-HT) is found in the gonads and accessory reproductive organs of several species. The golden (Syrian) hamster is a seasonal breeder. Exposure of male adult hamsters to short days for 14 weeks results in a severe gonadal regression, while after a photoinhibition period of 22 weeks a spontaneous testicular recrudescence occurs. The aim of this study was to investigate the presence of 5-HT and its major metabolite 5-hydroxyindoleacetic acid (5-HIAA) in the gonads of golden hamsters, its immunolocation and its physiological role in the testis. The influence of age and photoperiod was also analyzed. Hamsters of 23, 36, 46, 60 and 90 days of age were kept in long photoperiod (LP: 14:10 h light/dark), and adult animals were exposed either to LP or to short photoperiod (SP: 6:18 h light/dark) for 14 and 22 weeks. Testicular parenchyma and capsule levels of 5-HT and 5-HIAA increased significantly at ages of 36 and 60–90 days, but decreased markedly during the exposure of adult hamsters to SP for 14 and 22 weeks. Mast cells were found exclusively in the testicular capsule. The testicular number of mast cells increased concomitantly with age, but decreased in adult hamsters exposed to SP. Mast and Leydig cells presented 5-HT-positive immunoreactivity. During sexual maturation as well as during the transfer of adult hamsters from LP to SP, the 5-HIAA/5-HT ratio showed the highest values in active adult animals, indicating that the increase in testicular 5-HT levels in adulthood is accompanied by an augment in 5-HT turnover. In vitro basal and hCG-stimulated testosterone production was significantly inhibited in presence of physiological concentrations of 5-HT. In conclusion, the present studies demonstrate the existence of 5-HT in mast cells and Leydig cells of hamster testes, as well as describe an inhibitory action of this neurotransmitter on gonadal testosterone production. Furthermore, the age-dependent and photoperiodic-related changes detected in testicular 5-HT levels suggest that this neurotransmitter might act as an important local modulator of the action of gonadotropins on steroidogenesis during sexual development and during the photoperiodic regression-recrudescence transition in the golden hamster.
Mineralocorticoids and Glucocorticoids Cooperatively Increase Salt Intake and Angiotensin II Receptor Binding in Rat Brain
Authors: Shelat Suresh G. , King Jennifer L. , Flanagan-Cato Loretta M. , Fluharty Steven J.
Published: April 2003

Mineralocorticoids, such as deoxycorticosterone acetate (DOCA), and angiotensin II (AngII) act synergistically in the brain to elicit salt appetite. Glucocorticoids, such as dexamethasone (DEX), also may enhance the behavioral effects of DOCA and AngII. However, the brain regions involved in these behavioral interactions have not been elucidated. This study tested the hypothesis that DEX potentiates the effects of DOCA on AngII binding, especially at the AT1 receptor. We confirmed that DEX potentiated the effects of DOCA on salt appetite. Concomitantly, steroid-specific and region-specific changes in AT1 binding were noted. Specifically, in the hypothalamic paraventricular nucleus, treatment with DEX or DOCA + DEX increased AT1 binding. In the subfornical organ (SFO) and area postrema, there was an increase in AT1 binding when both steroids were combined, but not when given individually. However, there was no change in AT2 binding in any brain region studied and no change in AT1 or AT2 binding to either receptor subtype in the pituitary. The results indicate that DOCA and DEX may increase the sensitivity of the brain to the behavioral and physiological actions of AngII by upregulating AT1 receptors in the SFO and area postrema.
Effects of Experimental Hypothyroidism on 5-HT1A, 5-HT2A Receptors, 5-HT Uptake Sites and Tryptophan Hydroxylase Activity in Mature Rat Brain
Authors: Kulikov Alexander , Moreau Xavier , Jeanningros Régine
Published: April 2003

The study was aimed at investigating the repercussions of deficiency in thyroid function with and without thyroid hormone (TH) replacement on the neurochemical entities which underly serotonin (5-HT) neutrotransmission, namely 5-HT1A, 5-HT2A receptors, 5-HT transporter and tryptophan hydroxylase (TPH) in the mature brain. Surgically thyroidectomized male Wistar rats received: (1) an iodine-free diet to produce severe hypothyroidism; (2) hormonal replacement with 15 µg/kg/day of thyroxine (T4) for 21 days to normalize serum TH levels, or (3) hormonal replacement with 200 µg/kg/day of T4 for 14 days to produce an excess of circulating THs. Sham-operated rats were used as controls. Neither hypothyroidism nor an excess in serum TH levels affected 3H-8-OH-DPAT binding to 5-HT1A receptors, 3H-citalopram binding to 5-HT transporter and TPH activity in various brain structures indicating that, in the mature brain, the presynaptic entities of 5-HT neurotransmission are resistant to large variations in TH levels. By contrast, hypothyroid rats had a significant decrease in Bmax of 3H-ketanserin binding to cortical 5-HT2A receptors compared to controls. Cortical 3H-ketanserin binding in thyroidectomized rats was normalized after replacement with low-dose T4. Excess serum TH levels in thyroidectomized rats did not produce any changes in cortical 5-HT2A receptors when compared to thyroidectomized rats with normalized TH levels. The present data suggest that the decrease in cortical 5-HT2A receptors is the main neurochemical event underlying the impairing effect of hypothyroidism on 5-HT neurotransmission.
Development of a Site-Directed Polyclonal Antibody against the Pituitary Growth Hormone-Releasing Hormone Receptor and Its Use to Estimate GHRH Receptor Concentration in Normal and Hypothyroid Rats
Authors: Boulanger Luce , Andersen Peter H. , Gaudreau Pierrette
Published: April 2003

A site-directed polyclonal antipeptide antibody was generated in rabbits against segment 392–404 of the rat pituitary growth hormone-releasing hormone receptor (GHRH-R), using a multiple antigenic peptide system strategy of immunization. This C-terminal intracellular region of the rat GHRH-R exhibits 85% sequence identity with the human GHRH-R. The purified anti-GHRH-R(392–404) IgGs were characterized in cell lines expressing the human GHRH-R and in rat and human anterior pituitary, using immunoblotting. The polyclonal antibody recognized a 45-kD protein in human GHRH-R-transfected BHK 570 cell membrane preparations but not in wild-type cells. A 45-kD Nα-tagged human GHRH-R was immunodetected with both antitag and anti-GHRH-R antibodies in human GHRH-R-transfected HEK 293 cells. Cross-linking of [125I-Tyr10]hGHRH(1–44)NH2 to GHRH-R-transfected BHK cells led to the detection of a major and specific 45-kD radioactive complex. Its probing with the anti-GHRH-R(392–404) IgGs led also to the detection of a 45-kD entity. In rat anterior pituitary homogenates or membrane preparations, immunoblotting led to the detection of 44-, 47- and 65-kD proteins. In human anterior pituitary membrane preparations, immunoblotting led to the detection of 52- and 55-kD proteins. No immunoreactive signal was observed in the rat liver. Cross-linking of [125I-Tyr10]hGHRH(1–44)NH2 to rat anterior pituitary homogenates revealed the presence of specific 28-, 47- and 65-kD radioactive complexes. Probing of these radioactive complexes with the anti-GHRH-R(392–404) IgGs resulted in the visualization of 28-, 47- and 65-kD entities and of an additional immunoreactive 44-kD protein. To assess the usefulness of this GHRH-R antibody, estimation of changes in the concentration of rat anterior pituitary GHRH-R was performed by immunoblotting and compared to binding data after a 3-week antithyroid treatment. The treatment known to depress the 2.5- and 4-kb GHRH-R mRNA transcripts by at least 1.7-fold decreased the apparent maximal concentration of high (Bmax1) and low (Bmax2) affinity binding sites by 4.6- and 15.2-fold, respectively, and the 47- and 65-kD GHRH-R proteins by 3.5- and 1.25-fold, respectively. Altogether, the characteristics of the anti-GHRH-R(392–404) polyclonal antibody indicate that it specifically recognizes the human and rat GHRH-R. It also represents an additional valuable tool to estimate variations of GHRH-Rs in physiopathological conditions known to affect GHRH-R mRNA and/or GHRH binding site concentrations.
Identification of Endocannabinoids and Cannabinoid CB1 Receptor mRNA in the Pituitary Gland
Authors: González Sara , Manzanares Jorge , Berrendero Fernando , Wenger Tibor , Corchero Javier , Bisogno Tiziana , Romero Julián , Fuentes José A. , Di Marzo Vincenzo , Ramos José A. , Fernández-Ruiz Javier
Published: April 2003

Most data on effects of natural and synthetic cannabinoids on anterior pituitary hormone secretion point out to a primary impact on the hypothalamus. There is also some evidence, however, of possible direct actions of these compounds on the anterior pituitary, although the presence of cannabinoid receptors in the pituitary has not been documented as yet. In the present study, we evaluated the presence of cannabinoid CB1 receptor-mRNA transcripts in the pituitary gland by in situ hybridization. We observed CB1 receptor-mRNA transcripts in the anterior pituitary and to a lesser extent in the intermediate lobe whereas they were absent in the neural lobe. We then examined whether CB1 receptor-mRNA levels in both pituitary lobes responded to chronic activation by a specific agonist, as did receptors located in adjacent hypothalamic nuclei and in other brain regions. Daily administration of CP-55,940 for 18 days produced a small, but statistically significant paradoxical increase in CB1 receptor-mRNA levels in the anterior pituitary, with no changes in the intermediate lobe, in contrast to reduced CB1 receptor-mRNA levels observed in the ventromedial hypothalamic nucleus (VMN), and to decreased CB1 receptor binding in the VMN and the arcuate nucleus. The time-course of up-regulation of CB1 receptor-mRNA transcripts in the anterior lobe was biphasic; daily administration of Δ9-tetrahydrocannabinol produced an early and marked decrease in CB1 receptor-mRNA levels after 1 and 3 days, followed by normalization after 7 days and by a small increase after 14 days. We also checked whether endogenous cannabinoid ligands are present in the anterior pituitary and the hypothalamus. Although anandamide itself was detected only in trace amounts, concentrations of its precursor N-arachidonoyl-phosphatidyl-ethanolamine and of 2-arachidonoyl-glycerol were found in both tissues, suggesting that endocannabinoids may be synthetized in the anterior pituitary. In summary, CB1 receptors and corresponding ligands seem to be expressed in cells of the anterior and intermediate lobes of the pituitary, but the response of CB1 receptor-mRNA transcripts in the anterior lobe to chronic agonist activation is different than the desensitization observed in hypothalamic nuclei.
Sprague-Dawley Rats Obtained from Different Vendors Exhibit Distinct Adrenocorticotropin Responses to Inflammatory Stimuli
Authors: Turnbull Andrew V. , Rivier Catherine L.
Published: April 2003

The purpose of this work was to compare the plasma adrenocorticotropin (ACTH), corticosterone and interleukin-6 (IL-6) responses that rats of the outbred Sprague-Dawley strain obtained from two different vendors: Charles River (CR) and Harlan (HSD). Basal plasma ACTH and IL-6 concentrations were similar in rats from either vendor (HSD or CR), while CR animals exhibited slightly elevated corticosterone levels in late afternoon. Inflammatory stimuli such as lipopolysaccharide (LPS) (1 µg/kg, i.v.) or turpentine (50 µl/100 g, i.m.) which induce the production of endogenous cytokines, produced a significantly larger ACTH response in CR, compared to HSD rats, while the overall corticosterone responses were comparable in both rat groups. This could probably not be accounted for by a greater ACTH responsiveness in CR rats per se because CR and HSD rats showed similar peak ACTH responses to electrofootshock. Furthermore, in contrast to when the stimulus was one that induced endogenous cytokine production, the administration of exogenous interleukin-1β (IL-1β, 200 ng/kg, i.v.) produced a 2-fold greater rise in plasma ACTH concentrations in HSD rats compared to CR rats. The plasma IL-6 responses to the inflammatory stimuli showed a similar pattern to ACTH, with LPS and turpentine tending to pruduce greater IL-6 responses in CR rats, though these differences were not statistically significant. In contrast HSD rats had a significantly greater IL-6 response to IL-1β than did CR rats. Collectively, these results show that Sprague-Dawley rats obtained from different commercial sources can differ in immune-neuroendocrine responses to inflammatory stimuli.
Co-Localization of Growth Hormone Secretagogue Receptor and NPY mRNA in the Arcuate Nucleus of the Rat
Authors: Willesen Mette Georgi , Kristensen Peter , Rømer John
Published: April 2003

Growth hormone secretagogues (GHS) are small, synthetic compounds which have the potential of releasing growth hormone (GH) from the pituitary. The mechanism of action of GHS has not been fully elucidated. A specific GHS receptor (GHS-R) is expressed in the pituitary gland and in several areas of the brain including the hypothalamus. We have characterized the GHS-R-mRNA-expressing neurons with respect to co-expression of selected neurotransmitters in the hypothalamus. This was done by dual chromogenic and autoradiographic in situ hybridization with riboprobes for GHS-R mRNA and neuropeptide Y (NPY), pro-opiomelanocortin (POMC), somatostatin (SRIH) or GH-releasing hormone (GHRH) mRNA. In the arcuate nucleus, GHS-R mRNA was expressed in 94 ± 1% of the neurons expressing NPY, 8 ± 2% of those expressing POMC and 30 ± 6% expressing SRIH mRNA. 20–25% of the GHRH- mRNA-expressing neurons contained GHS-R mRNA, whereas the vast majority of the arcuate GHS-R-mRNA-containing cells did not contain GHRH mRNA. The finding of a significant co-expression of GHS-R and NPY mRNA in the arcuate nucleus is in accordance with the previous demonstration by Dickson et al. that c-Fos is induced in NPY neurons following GHS administration. These results indicate that GHS have other effects on neuroendocrine regulation than GH release via GHRH neurons. Stimulation of the arcuate NPY neurons via GHS-R may explain the increased appetite and the cortisol release seen after administration of some GHS compounds.
Neuronal Elements in the Testis of the Rhesus Monkey: Ontogeny, Characterization and Relationship to Testicular Cells
Authors: Frungieri Monica B. , Urbanski Henryk F. , Höhne-Zell Barbara , Mayerhofer Artur
Published: April 2003

Intrinsic neuron-like cells expressing the catecholamine-biosynthetic enzyme tyrosine hydroxylase (TH) were recently identified in the testis of the prepubertal rhesus monkey. In this study, we characterized the neuron-like nature of these cells and examined distribution and frequency of neuronal elements in the testes of monkeys during postnatal development, puberty and adulthood. Using immunohistochemical methods, we detected both nerve fibers and cell bodies, immunoreactive for the neuronal markers neurofilament 200 (NF-200) and synaptosomal associated protein of 25 kDa (SNAP-25), TH and neuropeptide Y (NPY) in perivascular locations, intermingled with interstitial cells and close to the wall of seminiferous tubules. Marked age-related differences in the numbers of these neuronal elements became apparent, when we quantified NF-200-immunoreactive neuronal elements. Thus, intrinsic neuron-like cell bodies were found only in the testes from immature animals (i.e., until about 3 years of age). Conversely, nerve fibers, presumably representing mainly the extrinsic innervation, were observed at all ages although they became more prominent after the pubertal increase in LH and testosterone levels. Interestingly, another testicular cell type known to contain potent regulatory substances, mast cells, was found to be in close anatomical proximity to nerve fibers. The number of these cells, positively identified with an antibody to tryptase, increased significantly after puberty following the same pattern as nerve fibers. These results confirm that the testicular nervous system of the monkey is composed of two components, intrinsic nerve cells and extrinsic fibers, both of which are catecholaminergic and peptidergic in nature. Furthermore, both components show a marked degree of plasticity during development, especially around the time of puberty. The intratesticular locations of neuron-like cells and fibers suggest that catecholamines and neuropeptides are likely to have multiple sites of actions, and may affect Leydig cells, cells of the tubular wall and vascular cells directly and/or indirectly via intermediation of mast cells.
Dopaminergic Agonists Normalize Elevated Hypothalamic Neuropeptide Y and Corticotropin-Releasing Hormone, Body Weight Gain, and Hyperglycemia in ob/ob Mice
Authors: Bina Keshavan G. , Cincotta Anthony H.
Published: April 2003

Hypothalamic neuropeptide Y (NPY) and corticotropin-releasing hormone (CRH) influence feeding and levels of plasma glucose, insulin, free fatty acids, and triglycerides. Treatment of genetically obese, ob/ob mice, with dopamine receptor D1/D2 agonists normalizes hyperphagia, body weight gain, hyperglycemia, and hyperlipidemia. We therefore examined whether levels of NPY and CRH immunoreactivity in discrete hypothalamic nuclei are altered in ob/ob mice, and whether dopaminergic treatment reverses this alteration. Female ob/ob mice were treated daily at 1 h after light onset with the D1/D2 agonists, SKF-38393 (20 mg/kg) and bromocriptine (15 mg/kg), respectively or vehicle for 2 weeks. Such treatment, while normalizing body weight gain and hyperglycemia, also significantly reduced elevated NPY immunoreactivity in the suprachiasmatic (by 39%), intergeniculate (by 43%), paraventricular (PVN; by 31%), and arcuate (by 41%) nuclei in obese mice to levels observed in lean mice. This treatment also caused a 45–50% decline in levels of CRH in the PVN and dorsomedial hypothalamus compared to obese controls to levels observed in lean mice. Taken together, these findings suggest that dopaminergic D1/D2 receptor coactivation may improve hyperphagia, hyperglycemia, and obesity in the ob/ob mouse, in part, by normalizing elevated levels of both NPY and CRH.
Recovery of the Hypothalamic-Pituitary-Adrenal Response to Stress
Authors: García Arantxa , Martí Octavi , Vallès Astrid , Dal-Zotto Silvina , Armario Antonio
Published: April 2003

Pathological consequences of stress-induced activation of the hypothalamic-pituitary-adrenal (HPA) axis may be related to the duration rather than to the intensity of HPA axis activation after exposure to the stressor. Consequently a fine analysis of post-stress events is of importance. The present experiments were designed to study the importance of three key factors in HPA recovery: intensity of the stressor (experiment 1), duration of exposure to the stressor (experiment 2) and previous experience of the animals with the situation (experiments 3 and 4). In experiment 1, analysis of both the response to the stressor and the poststress period showed that the stronger the stressor, the greater the area under the curve of HPA activation. In experiment 2, different groups of rats were exposed to different periods of immobilization (IMO) (20 min, 1 h and 2 h) and sampled before, during and after exposure to IMO. The speed of recovery of plasma corticotropin (ACTH) levels was not related to the duration of exposure to the stressor. In experiments 3 and 4, the influence of previous experience with the stressor was studied in rats daily exposed to 20 min IMO or daily injected with hypertonic saline (HS) for 8 days and sampled on days 1, 2, 5 and 8. Whereas a significant decline in plasma ACTH levels was not observed immediately after IMO until day 8, a single previous exposure to IMO was enough to enhance recovery 90 min after the end of exposure to IMO. Corticosterone levels were related to the number of previous experiences with the stressor only in the post-IMO period. In response to a novel stressor (forced swimming), chronic IMO rats showed a slightly impaired recovery as compared to stress-naive rats, suggesting that enhanced recovery of the HPA axis was specific for the homotypic stressor. After daily HS injections, a pattern similar to that after IMO was observed, the delayed, but not the early response of the HPA axis being reduced as a function of the number of previous experiences with the situation. Taken together, the present results suggest that the speed of recovery of the HPA axis after its activation by stressors is sensitive to the intensity of the stressors but not to their duration, and that adaptation to a repeated stressor is more apparent during the delayed HPA response.
Interactions of IGF-1 with the Blood-Brain Barrier in vivo and in situ
Authors: Pan Weihong , Kastin Abba J.
Published: April 2003

Insulin-like growth factor-1 (IGF-1) given peripherally has been found effective in clinical trials to slow down neuronal degeneration in some nervous system diseases. This raises the question of whether and how IGF-1 crosses the blood-brain barrier (BBB). In this report, we found that IGF-1 had a half-life of 4.5 min in blood, could remain intact for 20 min, and entered brain and spinal cord linearly. In the brain, IGF-1 had an influx rate of 0.4 µl/g·min after intravenous (iv) bolus injection as determined by multiple-time regression analysis. Intact radiolabeled IGF-1 was present in brain at 20 min after iv injection. Most of the injected IGF-1 entered the brain parenchyma instead of being entrapped in the cerebral vasculature. Addition of nonradiolabeled IGF-1 enhanced the influx of radiolabeled IGF-1 after iv injection, but inhibited the influx of radiolabeled IGF-1 by in-situ brain perfusion, suggesting that protein binding can explain the difference between the iv and perfusion experiments. In the spinal cord, the cervical region had the fastest uptake, followed by lumbar spinal cord. The thoracic spinal cord had the slowest uptake, comparable to that of brain. By contrast, des(1-3)IGF-1, an IGF-1 analogue with little protein binding but similar biological activity, had a shorter half-life in blood, slower influx rate into brain, and no alteration in pharmacokinetics after addition of nonradiolabeled peptide. We conclude that IGF-1 enters the CNS by a saturable transport system at the BBB, which functions in synchrony with IGF binding proteins in the periphery to regulate the availability of IGF-1 to the CNS.
Estrogen Increases Angiotensin II-Induced c-Fos Expression in the Vasopressinergic Neurons of the Paraventricular Nucleus in the Female Rat
Authors: Kisley Lori R. , Sakai Randall R. , Flanagan-Cato Loretta M. , Fluharty Steven J.
Published: April 2003

Previous studies in female rats have shown that estrogen treatment attenuates angiotensin II (AngII)-induced water intake. The mechanism underlying this attenuation may be decreased responsiveness to AngII, as revealed by a reduction in AngII binding to the angiotensin type 1 (AT1) receptor in the subfornical organ (SFO). It has not been determined whether these changes in receptor binding translate into changes in neuronal activity that, in turn, may influence behavior. Therefore, an estrogen-modulated change in neuronal pathways relevant to AngII-induced water intake was tested in ovariectomized (OVX) female rats using immunohistochemistry for the immediate early gene c-Fos as a marker for neuronal activation. Third cerebroventricular injection of AngII (6 ng) induced intense c-Fos immunoreactivity in forebrain regions associated with fluid intake, including the organum vasculosum of the lamina terminalis, the median preoptic nucleus, the SFO, the supraoptic nucleus and the paraventricular nucleus (PVN). Forty-eight-hour estradiol (10 µg) administration to OVX female rats increased AngII-induced c-Fos labeling in the lateral magnocellular neurons of the PVN by 30% as compared to vehicle-treated controls. Double labeling neurons in the PVN with c-Fos and either vasopressin or oxytocin antisera revealed that estrogen increased AngII-induced c-Fos expression by 28%, specifically in vasopressinergic neurons. Such changes in neuronal activation may explain the estrogen modulation of AngII-induced water intake that has been previously reported; it may be due to increased water retention to maintain plasma osmolality or to induction of a pressor response.
Effects of Leptin and Corticosterone on the Expression of Corticotropin-Releasing Hormone, Agouti-Related Protein, and Proopiomelanocortin in the Brain of ob/ob Mouse
Authors: Arvaniti Konstantinia , Huang Qingling , Richard Denis
Published: April 2003

The present study was conducted to assess the effect of leptin and corticosterone on the expression of corticotropin-releasing hormone (CRH), proopiomelanocortin (POMC) and agouti-related protein (AGRP) in the mouse brain. To this end, a 3 × 3 factorial experiment was designed in which adrenalectomized (ADX) ob/ob mice were treated with leptin and corticosterone. Leptin and corticosterone downregulated CRH expression in the paraventricular hypothalamic nucleus (PVH). Leptin prevented the stimulating effects of ADX on the expression of CRH and the combination of small doses of leptin and corticosterone was as potent as the high dose of corticosterone in suppressing CRH mRNA expression in the PVH. Leptin and corticosterone enhanced the expression of CRH in the central nucleus of amygdala and in the bed nucleus of the stria terminalis. In addition, the present results confirmed the downregulating effects of leptin on the expression of AGRP mRNA in the hypothalamic arcuate nucleus (ARC), and demonstrated that this effect was more apparent in ADX mice treated with corticosterone than in ADX mice not supplemented with corticosterone. Also, leptin and corticosterone had opposite effects on the expression of POMC in the ARC. The opposite effect of leptin and corticosterone on the expression of POMC and AGRP seems consistent with the reported effects that these hormones and peptides have on food intake and thermogenesis, suggesting that the modulation of POMC and AGRP expression can be a mechanism whereby leptin and corticosterone exert their effects in the regulation of energy balance. In contrast, the similarity in the action of leptin and corticosterone is not a priori consistent with a role of CRH in the effects of these hormones in the regulation of energy balance. The downregulating effect of leptin on the expression of CRH in the PVH strongly suggests that leptin can be a potent regulator of hypothalamic-pituitary-adrenal axis activity. Finally, the present results suggest that the effects of leptin on the expression of CRH, POMC and AGRP are not curbed by glucocorticoids.
Low Leptin Levels but Norma Body Mass Indices in Patients with Depression or Schizophrenia
Authors: Kraus Thomas , Haack Monika , Schuld Andreas , Hinze-Selch Dunja , Pollmächer Thomas
Published: April 2003

Appetite, food intake and weight are frequently altered in psychiatric disorders such as major depression and schizophrenia. The few studies investigating weight and the body mass index (BMI) have yielded variable results. Leptin, a fat cell-derived hormone signalling to the brain the size of the adipose tissue, plays a pivotal role in the regulation of weight and food intake. Moreover, leptin is involved in the control of other behaviors and in brain development. There is almost no information about the amounts of circulating leptin in major depression or schizophrenia. We investigated the BMI and plasma leptin levels in patients with major depression (n = 62), schizophrenia (n = 42), and in healthy controls (n = 64). Mean BMIs did not differ between groups. However, leptin levels were significantly lower in both patient groups compared to healthy controls. Moreover, patients suffering from schizophrenia showed significantly lower leptin levels than depressed patients. Decreased leptin levels were independent of psychotropic medication. We conclude that depression and schizophrenia go along with decreased systemic leptin concentrations that cannot be explained by medication or an altered BMI. Hence, leptin might play an important pathophysiological role in these psychiatric disorders that deserves further scientific attention.
A Short Period of Maternal Nutrient Restriction in Late Gestation Modifies Pituitary-Adrenal Function in Adult Guinea Pig Offspring
Authors: Lingas Rania I. , Matthews Stephen G.
Published: April 2003

Altered fetal environment can program the hypophyseal-pituitary-adrenal (HPA) axis development and thus affect endocrine function in later life. We hypothesized that 48 h of maternal nutrient restriction during the period of maximal fetal brain growth alters HPA function in adult offspring and leads to modified blood pressure regulation. Pregnant guinea pigs (n = 15) were deprived of food (water ad libitum) or fed normally (n = 13) on days 50 and 51 of gestation, after which they were all fed normally (birth = 68 days). Carotid artery and jugular vein catheters were implanted in adult guinea pig offspring (day 65). Animals were treated with corticotropin (ACTH1–24; 0.5 µg/kg), corticotropin-releasing hormone (CRH; 0.5 µg/kg) and insulin (5 units/kg), and pituitary-adrenal responses were measured. Guinea pigs were then euthanized and pituitaries removed for analysis of pro-opiomelanocortin (POMC) and glucocorticoid receptor (GR) mRNA levels. There was no effect of prenatal treatment on body weight, blood pressure or heart rate. In male offspring, both basal ACTH (p < 0.007) and basal cortisol (p < 0.05) levels were significantly reduced in animals whose mothers had been nutrient restricted (NR). In contrast, in female offspring, basal plasma ACTH was not different between offspring from NR mothers and controls; however, basal plasma cortisol concentrations were significantly (p < 0.01) elevated at 13.00 h in females born to NR mothers. Responses to HPA challenge were different between offspring from NR mothers and control offspring, and these differences were consistent with alterations in basal adrenocortical function. There was no effect of prenatal treatment on POMC mRNA levels in the pars distalis or pars intermedia. However, GR mRNA levels were significantly (p < 0.05) reduced in adult female offspring born to NR mothers. In conclusion, 48 h of maternal nutrient restriction during pregnancy has a long-term effect on HPA function in adult offspring, and this effect is highly sex specific, but does not result in alteration of blood pressure.