bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cholecystokinin Activates C‐Fos Expression in Hypothalamic Oxytocin and Corticotropin‐Releasing Hormone Neurons
Authors: Verbalis Joseph G. , Stricker Edward M. , Robinson Alan G. , Hoffman Gloria E. 
Published: September 2006

AbstractThe effect of systemically‐administered Cholecystokinin octapeptide (CCK) on hypothalamic oxytocin, vasopressin, and corticotropin‐releasing hormone neurons was studied by analysis of c‐fos antigen expression in immunocytochemically‐characterized neurons in the supraoptic and paraventricular nuclei. CCK (100μg/kg intraperitoneally) caused a marked increase in nuclear c‐fos immunocytochemical staining, which peaked at 60 to 90 min after injection. C‐fos expression was found in most magnocellular oxytocin neurons in the supraoptic nucleus and in all magnocellular subdivisions of the paraventricular nucleus, but in no vasopressin neurons in either area. C‐fos expression was also found in several parvocellular subdivisions of the paraventricular nucleus: in oxytocin neurons within the medial and lateral, but not the dorsal, parvocellular subdivisions, and in corticotropin‐releasing hormone neurons in the medial parvocellular subdivision. Injection of lower doses of CCK showed that c‐fos expression closely paralleled the pattern of pituitary oxytocin secretion in response to CCK, with a threshold for activation at 1 μg/kg, near maximal responses by 10 μg/kg, and maximal responses by 100 μg/kg. These studies demonstrate that the pattern of c‐fos expression in hypothalamic magnocellular neurons following systemic CCK administration mirrors the neurosecretory response of these neurons, both with regard to specificity for the peptides secreted as well as intensity of secretion. They also demonstrate that systemic CCK administration activates c‐fos expression in parvocellular oxytocin and corticotropin‐releasing hormone neurons, and therefore likely causes secretion of oxytocin and corticotropin‐releasing hormone within the brain at the terminal fields of these neurons.
Generation and Characterization of an Antiserum Directed Against Neurohypophyseal Prohormones
Authors: Verbalis Joseph G. , Hoffman Gloria E. , Rosenbaum Lawrence C. , Nilaver Gajanan , Loh Y. Peng 
Published: September 2006

AbstractAn antiserum to neurohypophyseal prohormones was generated by immunization of rabbits with a synthetic peptide fragment bridging the prohormone cleavage site between the vasopressin (AVP) and human AVP‐neurophysin sequences of pro‐pressophysin. Polyclonal antibodies directed against this peptide cross‐reacted with intact human pro‐pressophysin (ED50 of 260fmol), but not with either of the final products of enzymatic processing, AVP and human AVP‐neurophysin. Gel electrophoresis and Western immunoblotting of pituitary or hypothalamic extracts from multiple species including mouse, cow and man identified a protein band of molecular weight consistent with intact pro‐pressophysin; in hypothalamic extracts from normally‐hydrated rats no protein bands were stained, but in extracts from Brattleboro rats a faint band in the area of pro‐oxyphysin was identified. Immunohistochemical studies using the antiserum demonstrated the presence of only very small amounts of immunoreactive prohormone in a few widely scattered cells in the hypothalami of normally‐hydrated rats. However, after 5 days of solute loading with 2% NaCl as drinking solution, staining for intact prohormone was prominent in the supraoptic and paraventricular nuclei of the hypothalamus. Combined immunoperoxidase‐immunofluorescence labeling for prohormone and either AVP‐neurophysin or oxytocin‐neurophysin revealed prohormone staining in both types of magnocellular neurons in rat hypothalami. These studies suggest that during states of accelerated synthesis and secretion of neurohypophyseal hormones some accumulation of intact prohormone occurs in both AVP and oxytocin magnocellular neurons.
Acetylcholine Synthesis in a Primary Culture of Porcine Intermediate Lobe Cells
Authors: Tandon A. , Collier B. , Zhang Z. W. , Feltz P. 
Published: September 2006

AbstractPrevious pharmacological studies with the pituitary gland have suggested that acetylcholine (ACh) might be involved in the regulation of intermediate lobe (IL) function. Whether ACh is endogenous to the IL cells or provided from an extrinsic source is unclear. The present experiments tested the possibility that the endocrine cells of the IL may be a source of ACh by measuring certain cholinergic markers in a primary culture of dissociated porcine cells. The endogenous ACh content was readily measurable in both the freshly dissociated IL cells and in 2‐ or 4‐day primary cultures. Choline acetyltransferase activity was also measurable in the freshly dissociated and cultured IL cells and was reduced by 53% in the presence of a specific inhibitor, napthylvinylpyridine (50 μM). IL cells incubated in the presence of [14C]choline (1 μM) were able to synthesize [14C]ACh and the accumulation of the new ACh was inhibited by hemicholinium‐3 (30 μM), a competitive inhibitor of high affinity choline uptake at cholinergic nerve terminals. In conclusion, these results demonstrate that the endocrine cells of the IL are capable of synthesizing and storing ACh.
Effect of Ovariectomy or Oestrogen Implants upon Pituitary Function in Female Hypogonadal Mice Bearing Normal Fontal Preoptic Area Grafts
Authors: Scott I. S. , Goff A. E. Porter , Cox B. S. , Charlton H. M. , Clayton R. N. 
Published: September 2006

AbstractThe effects of ovariectomy and oestrogen feedback for 10 days upon pituitary and serum luteinizing hormone (LH) content, pituitary glycoprotein subunit messenger ribonucleic acid (mRNA) and prolactin mRNA content in normal females, female hypogonadal mice and hypothalamic grafted female hypogonadal mice, bearing a graft of normal mouse preoptic area tissue into the third ventricle, have been investigated. In normal females ovariectomy resulted in a rise in serum LH, LHβ‐subunit and common α‐subunit mRNAs with no significant change in pituitary LH content or follicle‐stimulating hormone (FSH) β‐subunit mRNA. In the hypogonadal females, preoptic area grafting resulted in an elevation in all of the above parameters into the normal range. Ovariectomy in this group resulted in a further elevation of serum LH, LHβ‐subunit and α‐subunit mRNAs with no change in pituitary LH content or FSHβ‐subunit mRNA, which in all cases were comparable to ovariectomized normal animals. Oestrogen treatment caused a fall in pituitary LH content and the serum LH fell below the detection of the assay. LHβ‐subunit and a‐subunit mRNA mirrored this fall but there was no change in FSHβ‐subunit hybridization. These experiments suggest that even though normal neuronal input to the gonadotrophin‐releasing hormone neurons is disrupted, oestrogen‐induced negative feedback can still occur in grafted female hypogonadal animals. Gonadotrophin‐releasing hormone neurons are reported to lack oestrogen receptors but feedback within this graft by co‐transplanting oestrogen‐sensitive neurons remains a possibility, as does feedback at the level of the host median eminence where graft axons extend to the pituitary portal vessels. The similarity of the response in normal and grafted animals indicates that these actions of oestrogen may be effected predominantly at the pituitary level.
Functional Interrelationships Between Adrenergic and Opioid Systems in the Neuroregulation of Growth Hormone Secretion in Infant Rats
Authors: Arce Victor M. , Cella Silvano G. , Locatelli Vittorio , Müller Eugenio E. 
Published: September 2006

AbstractFunctional interrelationships between hypothalamic adrenergic and opioid systems were studied in 10‐day‐old male and female rats. Either clonidine (150 μg/kg, sc), an α2‐adrenoceptor agonist, or FK 33‐824 (1 mg/kg, sc), a synthetic analog of met‐enkephalin, increased plasma growth hormone (GH) levels, the increment being significantly higher with FK 33‐824 than with clonidine. Pharmacologic blockade of opioid receptors with naloxone (5 mg/kg, sc) did not modify either basal GH levels, or the GH response to clonidine, whereas blockade of α2‐adrenoceptors with yohimbine (2.5 mg/kg, sc) reduced basal GH levels and partially counteracted the FK 33‐824‐induced GH rise. Clonidine (150μ/kg, sc, twice daily) administered from postnatal day 5 to 9, increased basal GH levels and pituitary GH content. In these pups, acute administration of clonidine failed to further release GH, but the GH response to acute administration of FK 33‐824 was significantly enhanced. A 5‐day treatment with FK 33‐824 (1 mg/kg, sc, twice daily), neither modified basal GH levels, nor pituitary GH content. Under these conditions, the in vivo GH response to an FK 33‐824 challenge was significantly enhanced, and the response to clonidine was preserved. Pituitaries from FK 33‐824‐pretreated rats were hyperresponsive to GH‐releasing hormone (10−7 M).In summary, our data indicate that in rat pups: 1) two separate components i.e. one adrenergic, the other extra‐adrenergic, subserve the GH‐releasing effect of opioid peptides; 2) in contrast to short‐term stimulation of α2‐adrenoceptors, stimulation of opioid receptors does not trigger GH synthesis or induce down‐regulation or tolerance; 3) short‐term opioid stimulation does not affect an α2‐adrenergic challenge, but sensitizes to an opioid challenge.
Endogenous Opioids Modulate the Oxytocin Response to Insulin‐Induced Hypoglycaemia and Partially Mediate the Inhibitory Effect of Ethanol in Man
Authors: Coiro V. , Capretti L. , Davoli C. , SperoniJ G. , Bianconi L. , Cavazzini U. , Marcato A. , Papadia C. , Volpi R. , Chioderat P. 
Published: September 2006

AbstractThe possible inhibition exerted by ethanol on the oxytocin (OT) response to insulin‐induced hypoglycaemia was tested in man. Furthermore, the possibilities that endogenous opioids play a role in the control of hypoglycaemia and/or ethanol action on OT were examined. Insulin tolerance tests were performed in three groups of eight age‐ and weight‐matched normal men treated with: 1) naloxone, group 1 1 mg bolus naloxone + 2.5 mg over 105 min, group 2 2 mg bolus naloxone + 5 mg over 105 min, group 3 4 mg bolus naloxone + 10 mg over 105 min; 2) ethanol (50 ml in 110ml of whiskey) to all the groups; 3) a combination of ethanol + naloxone; 4) normal saline. Furthermore, the effect of ethanol + naloxone (4+10mg) in the absence of insulin‐induced hypoglycaemia was evaluated in seven additional subjects. During this latter test, the plasma levels of OT remained unchanged. Insulin‐induced hypoglycaemia produced a 2.2‐fold increment in plasma OT levels in the control experiments. This response was not changed by the treatment with the lowest dose of naloxone (1+2.5mg) in group 1, but it was significantly enhanced by administration of naloxone at higher doses (mean peak OT levels rose 2.8‐fold in both group 2 and group 3). In all subjects the OT response to hypoglycaemia was completely abolished by ethanol. However, when ethanol was given together with naloxone, the hypoglycaemia‐induced OT rise was only partially inhibited by ethanol. At all doses naloxone produced similar effects; in fact, in all groups OT rose 1.5‐fold in response to hypoglycaemia during insulin tolerance test + ethanol + naloxone. Neither naloxone nor ethanol altered the basal secretion of OT, as tested during 45 min before the insulin tolerance test.These data demonstrate that the OT response to insulin‐induced hypoglycaemia is inhibited by ethanol. Furthermore, the data indicate that endogenous opioids are involved in the control of hypoglycaemia‐stimulated OT secretion and partially modulate ethanol inhibitory action.
Glutamate Peripherally Administered Exerts Somatostatin‐Releasing Action in the Conscious Rat
Authors: Benyassi Ahmed , Tapia‐Arancibia Lucia , Arancibia Sandor 
Published: September 2006

AbstractThis study was designed to determine whether glutamate is able to stimulate somatostatin release from in vivo conscious animals when somatostatin release is monitored in unanaesthetized rats stereotaxically implanted with a push‐pull cannula in the median eminence. One week after implantation, the median eminence was perfused with artificial cerebrospinal fluid alone or with the addition of either CGS 19755, an N‐methyl‐D‐aspartate (NMDA) receptor antagonist (1(10−6 M), or glutamate (10−5 M). The latter (which is able to cross the brain‐blood barrier at large doses) was also peripherally administered (1 g/kg ip). Median eminence perfusate samples were collected every 15 min and somatostatin was measured by a sensitive radioimmunoassay.In rats receiving ip glutamate injection, somatostatin release from the median eminence was significantly increased (73.3±10.4 versus 24.8 ± 6.2; P < 0.01; n = 5) when compared to baseline levels measured in the same animals, but no effect was observed when local perfusion of the median eminence with glutamate (10−4 to 10−5 M; n = 6) was performed. Glutamate‐induced somatostatin release was completely blunted (n = 5) by prior local administration of CGS 19755 (10−5 M), a potent NMDA‐type receptor antagonist able to cross the blood‐brain barrier. In contrast, administration of glutamic acid diethylester, a competitive antagonist of non‐NMDA receptors, at doses of 10−4 M (n = 4), was not able to alter this response.Our results are the first in vivo evidence in favour of a neuroendocrine role for glutamate on somatostatin release whose site of action seems to exclude the median eminence.
The Influence of Photoperiod on the Hypothalamic Content of Beta‐Endorphin and the Luteinizing Hormone Responses to Naloxone and to Steroid Withdrawal in the Male Syrian Hamster
Authors: Juss T. S. , Maywood E. , Walker A. P. , Herbert J. , Hastings M. H. 
Published: September 2006

AbstractThe aim of this study was to investigate the influence of inhibitory photoperiods upon opioidergic function, as determined by changes in the hypothalamic content of β‐endorphin and the luteinizing hormone response to opioidergic receptor blockade, in the male Syrian hamster over the course of gonadal involution and spontaneous gonadal recrudescence. Animals exposed to an 8 h light: 16 h dark cycle (8L: 16D) for 14 weeks underwent gonadal regression. Regression was also observed in animals held for 7 weeks on one of a range of short daylengths of between 11.5 h and 13.5 h, the degree of atrophy being greatest in those animals on the shortest daylength. The tissue concentration of β‐endorphin within the mediobasal hypothalamus was significantly higher in animals exposed to 8L: 16D for 14 weeks than in gonadally active controls held on long days (16L: 8D). Exposure to photoperiods of less than 13.5 h for 7 weeks also caused a significant increase in the β‐endorphin content of the mediobasal hypothalamus and there was a positive correlation between the concentration of β‐endorphin, the degree of gonadal atrophy and the shortness of the photoperiod. Endorphin levels within the preoptic area were not affected by photoperiodic treatments.Exposure of intact animals to 8L: 16D for 12 weeks caused gonadal atrophy and an associated loss of the luteinizing hormone responses to both naloxone and castration. Castrated animals receiving testosterone replacement (cast + T) also exhibited photoinhibition, in the form of reduced serum levels of luteinizing hormone, and this was similarly accompanied by a loss of sensitivity to naloxone and to withdrawal of steroid. Prolonged exposure to 8L:16D led to spontaneous reactivation of the gonadotrophic axis as a consequence of the development of scotorefractoriness. In both gondally intact animals and in cast + T groups, this was associated with a restoration, in parallel, of the luteinizing hormone responses to naloxone and to castration/ steroid withdrawal. The time‐course of the restoration of the response to steroid withdrawal in castrates was not significantly different to that observed in intact animals. The luteinizing hormone response to naloxone took significantly longer to redevelop in cast + T groups than it did in gonadally intact animals.The data demonstrate that central opioid systems are sensitive to photoperiod and are consistent with the hypothesis that opioids are involved in the neuroendocrine regulation of reproductive responses to daylength.
Involvement of Dopamine in Inhibition of Food Intake by Cholecystokinin Octapeptide in Male Rats
Authors: Bednar I. , Forsberg G. , Lindén A. , Qureshi G. A. , Södersten P. 
Published: September 2006

AbstractDeprivation of food reduced the level of dopamine in the cerebrospinal fluid of male rats and subsequent ingestion of food or intraperitoneal injection of Cholecystokinin octapeptide restored the level. Injection of a dopamine receptor agonist (apomorphine) or Cholecystokinin octapeptide inhibited food intake and these effects were reversed by pretreatment with a dopamine receptor antagonist (cis‐flupentixol). Blockade of cholecystokinin‐A receptors, by treatment with L‐364,718, but not cholecystokinin‐B receptors, by treatment with L‐365,260, blocked the inhibitory effect of Cholecystokinin octapeptide on food intake but did not affect the inhibitory effect of apomorphine. It is suggested that Cholecystokinin interacts with dopamine in the control of food intake.
Mapping of the Bovine Oxytocin Gene Control Region: Identification of Binding Sites for Luteal Nuclear Proteins in the 5′ Non‐Coding Region of the Gene
Authors: Walther Norbert , Wehrenberg Uwe , Brackmann Beate , Ivell Richard 
Published: September 2006

AbstractIn view of the small number of hormone‐producing cells, the factors regulating oxytocin gene expression in the classic site of synthesis, in the magnocellular neurons of the hypothalamus, have not yet been characterized. In the early bovine corpus luteum there is a tissue‐specific oxytocin expression involving many more cells. This tissue therefore was chosen as a experimental system to identify deoxyribonucleic acid elements and nuclear proteins involved in the regulation of oxytocin gene expression. 3.2 kb from the 5’non‐coding region of the bovine oxytocin gene have been sequenced and subcloned fragments used as probes for gel retardation and footprinting experiments. Binding sites for luteal as well as more ubiquitous proteins were detected in the oxytocin promoter region and in an artiodactyl‐specific dispersed repeated deoxyribonucleic acid element. A binding site in the promoter region with a superficial similarity to an estrogen‐responsive element (‐159 to ‐152) was shown not to bind this steroid hormone receptor but to bind two nuclear proteins alternatively. One is a luteal protein, the other a more general transcription factor belonging to the steroid hormone receptor superfamily and similar, if not identical to the COUP protein. This alternative binding of a tissue‐ and phase‐specifically expressed protein or an ubiquitous factor to the same site in the oxytocin promoter suggests a role for these two proteins in the transient up‐regulation and subsequent down‐regulation of the oxytocin gene during the differentiation of the bovine corpus luteum.
Long‐Term Dynamic in vitro System for Investigating Rat Pineal Melatonin Secretion
Authors: Rékési Z. , Csernus V. , Horvéth J. , Vigh S. , Mess B. 
Published: September 2006

AbstractSeveral details regarding the control of melatonin (MT) secretion from the pinealocytes are still to be clarified. To obtain more data on the mechanism and kinetics of MT secretion and on the interactions between bioactive materials affecting MT production, a perifusion system has been developed in our laboratory. In this dynamic in vitro system the surviving pinealocytes maintain their full responsiveness for at least 5 days. In order to determine the MT contents of large numbers of samples collected in the perifusion system, a sensitive MT radioimmunoassay was set up utilizing our specific MT antibody.In our perifusion system the basal MT release does not change significantly during the 5‐day experiments. Norepinephrine (NE) was used at 1 μM concentration for 30 min as a marker of the responsiveness of pinealocytes, given at the beginning and at the end of the same experiments. No significant difference was found in the MT responses to NE stimulation over 5 days.The kinetics of MT response and the dose‐response relationship were investigated after NE exposure at various concentrations (100 nM to 10 mM). NE at 100 nM was found to be ineffective. Between 1 μM and 1 mM concentrations NE increased the MT release in a dose‐dependent manner. No significant difference was found between the responses above 1 mM concentration. NE seems to be a specific stimulator of pineal MT production.The MT production reached the maximum value after a relatively long lag (2 to 3 h) when NE application had been stopped, and returned to basal values after 5 to 6 h. This prolonged time‐course of MT secretion, in contrast with the fast responses of pituitary cells to releasing hormones, suggests that NE stimulated the synthesis of MT rather than the release of stored hormone.The modulatory effects of light‐dark cycle on basal and stimulated MT release of perifused pineals was also investigated: Neither basal nor NE‐stimulated (100 nM to 10μM) MT release was influenced significantly by light‐dark conditions showing that the light‐dark cycle does not have a direct modulatory effect on MT secretion under in vitro circumstances.Based on our observations, this perifusion system should be a useful tool for investigating: 1) hormone interactions on the regulation of pineal MT release, and 2) accurate kinetics of MT response.
Angiotensin Peptides in Brain and Pituitary of Rat and Sheep
Authors: Lawrence Anne C. , Clarke Lain J. , Campbell Duncan J. 
Published: September 2006

AbstractSeveral lines of evidence indicate that angiotensin peptides may be formed in the brain, where angiotensin II (Ang II) and angiotensin‐(1–7) (Ang‐(1–7)) may function as neurotransmitters. However, there is considerable controversy concerning the identity and levels of angiotensin peptides in the brain. We have used a novel high performance liquid chromatography‐based radioimmunoassay to measure Ang‐(1–7), Ang II, Ang‐(1–9) and Ang I in various brain regions and in the pituitary of the rat and sheep. We also studied the effect of different methods of tissue extraction, and the effect of the converting enzyme inhibitor ramipril, on angiotensin peptide levels in the rat hypothalamus. The levels of Ang‐(1–7), Ang II, Ang‐(1–9) and Ang I were low (<25 fmol/g) in all brain regions examined, except for the sheep median eminence and cerebellar cortex where Ang II levels were 385±116 and 193±37 fmol/g (mean ± SEM, n = 6), respectively. Pituitary Ang II levels were 103±13 fmol/g in the rat and 63±18 fmol/g in the sheep. The levels of Ang‐(1–7), Ang‐(1–9) and Ang I were much lower than those of Ang II in brain and pituitary. Ang‐(1–7) levels in the rat hypothalamus were low (<6 fmol/g) but methods of extraction which involved freezing and thawing of the tissue resulted in substantially higher levels of this peptide. Ang II levels in the rat hypothalamus (18±3 fmol/g) were reduced to undetectable levels (<6 fmol/g) by ramipril administration. The low levels of angiotensin peptides in the hypothalamus and brainstem indicate that if these peptides function as neurotransmitters in these regions, then they are of particularly low abundance. Moreover, our results indicate that the high levels of Ang‐(1–7) reported previously for rat hypothalamus may be artefactual, due to the method of tissue extraction.