bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ibotenate Lesions of the Diagonal Band of Broca Attenuate Baroreceptor Sensitivity of Rat Supraoptic Vasopressin Neurons
Authors: Cunningham J. Thomas , Nissen Ralph , Renaud Leo P. 
Published: September 2006

AbstractPrevious electrophysiological studies in the rat suggest that neurons in the diagonal band of Broca participate in baroreceptor‐induced suppression of the spontaneous activity of vasopressin‐secreting neurons in the hypothalamic supraoptic nucleus. In order to test this hypothesis, extracellular recordings were obtained from phasically‐active vasopressin neurons in the supraoptic nucleus of anesthetized rats injected at least 3 days previously with ibotenic acid (1.25 μg/250 nl) in the diagonal band of Broca, the medial and lateral septum, or the median preoptic nucleus. In normal rats, brief increases in blood pressure produced by injections of metaraminol (10 μg/10 μl iv) that were sufficient to activate peripheral baroreceptors, suppressed the activity of a majority (21 tested, 19 suppressed) of phasically‐active vasopressin‐secreting neurons. In rats with ibotenic acid lesions of the diagonal band of Broca, the number of phasically‐active neurons that were baroreceptor‐sensitive was significantly reduced (21 tested, 8 suppressed) while lesions of the medial and lateral septum (17 tested, 16 suppressed) or the median preoptic nucleus (21 tested, 20 suppressed) had no effect. The results support the hypothesis that diagonal band of Broca neurons participate in a central pathway mediating the inhibitory effects of peripheral baroreceptor stimulation on the activity of vasopressin‐secreting neurons in the rat supraoptic nucleus.
Hypothalamic Effects of C‐Type Natriuretic Peptide on Luteinizing Hormone Secretion
Authors: Huang Fong‐Lee S. , Skala Karl D. , Samson Willis K. 
Published: September 2006

AbstractPrevious studies have demonstrated hypothalamic sites of action of A‐type natriuretic peptide (ANP) in the inhibition of luteinizing hormone (LH) secretion, acting at least in part, via an opiatergic mechanism. C‐type natriuretic peptide (CNP) was identified recently and is thought to be the predominant brain form of the family of natriuretic peptides. Third cerebroventricular injection of CNP in doses of either 0.1, 1.0 or 2.0 nmole significantly inhibited, in a dose‐related fashion, plasma LH levels when compared to levels present in saline‐injected controls. When compared to the LH‐inhibiting action of ANP, CNP appeared more potent (effective at lower doses) and efficacious (longer duration of action for the maximum effective doses). The LH‐inhibiting effect of CNP was blocked by prior treatment with the δ‐opioid receptor antagonist naltrindole (50 μg), suggesting an enkephalinergic mechanism of action. CNP in log doses ranging from 0.01 to 1,000 nM did not significantly alter LH release from dispersed pituitary cells harvested from random cycle female rats, either under static or dynamic (perifusion) incubation conditions. These results indicate that CNP, like ANP, acts at the hypothalamic level to alter LH secretion and suggest that CNP may be the preferential neuroactive members of this family of peptides.
Pineal Photoreceptor Cells: Photoperiodic Control of Melatonin Production After Cell Dissociation and Culture
Authors: Bégay Valérie , Falcón Jacky , Thibault Christèle , Ravault Jean‐Paul , Collin Jean‐Pierre 
Published: September 2006

AbstractTrout pineal cells were dissociated using a trypsin‐DNase digestion technique. An enriched population of photoreceptor cells was selected from a Percoll gradient centrifugation. The ability of cultured photoreceptor cells (selected or not on a Percoll gradient) to produce melatonin rhythmically was investigated during seven 24 h light/dark cycles. During each cycle, trout pineal photoreceptor cells released low amounts of melatonin during daytime and high amounts during night‐time. Under continuous darkness, melatonin release was continually high. The profile of its rhythm and that of the activity of the hydroxyindole‐O‐methyltransferase—the last enzyme of the melatonin biosynthetic pathway—depended on the substrates and on the culture media used. Some of them appear suitable for short‐ or long‐term culture of photoreceptor cells permitting the study of their neuroendocrine properties.
Developmental Aspect of Differences in Hypothalamic Preproneuropeptide Y Messenger Ribonucleic Acid Content in Lean and Genetically Obese Zucker Rats
Authors: Sanacora Gerard , Finkelstein Judith A. , Whitet Jeffrey D. 
Published: September 2006

AbstractThe genetically obese Zucker rat is a well characterized model of early onset human obesity. Many of the endocrine and metabolic abnormalities of obese animals are common to other strains of genetically obese animals as well as morbidly obese humans. Neuropeptide Y (NPY), a potent orexigenic agent, was recently found to be elevated in adult obese animals compared to their lean littermates. In this study we first examined hypothalamic expression of preproNPY mRNA, using solution hybridization/ nuclease protection analysis, in phenotypically‐matched, i.e. lean or obese, immature (5‐week‐old) and mature (33‐week‐old) animals. Although changes were not statistically different, a trend toward decreased hypothalamic preproNPY mRNA levels was detected in both lean and obese mature animals. We next compared hypothalamic preproNPY mRNA levels between age‐matched lean and obese animals at 5, 14 and 33 weeks of age and found elevated preproNPY mRNA levels in obese rats at all three ages. These data suggest that increased levels of hypothalamic NPY are an early manifestation of the obese phenotype and may, therefore, contribute to hyperphagia and increased weight gain in obese Zucker rats.
Regulation of Prolactin Messenger Ribonucleic Acid Levels by Estradiol and Dihydrotestosterone as Evaluated by in situ Hybridization Performed on Implanted Pituitary Glands and Anterior Pituitary Cells in Culture in the Male Rat
Authors: Tong Yiai , Veilleux Raymonde , Pelletier Georges 
Published: September 2006

AbstractWe have recently demonstrated that 17ß‐estradiol (E2) administration increases protactin (PRL) mRNA levels in the male rat anterior pituitary gland and that this stimulatory effect is partially inhibited by concomitant administration of dihydrotestosterone. In order to gain more information about the site(s) of action of E2 and dihydrotestosterone on PRL gene expression, we have studied the effects of these two hormones in pituitaries implanted under the kidney capsule as well as in anterior pituitary cells in culture. In implanted pituitaries, PRL mRNA levels were increased by 90% as compared to values obtained in the stalk‐connected pituitaries from the same animals. Administration of E2 induced a further increase of PRL mRNA levels in implanted pituitaries, while dihydrotestosterone did not produce any change in animals which had been treated or not with E2. In anterior pituitary cells in culture, addition of E2 to the culture medium resulted in a 60% increase of PRL mRNA levels over control values. Supplementation with dihydrotestosterone did not induce any variation in the concentration of PRL mRNA in cells which were treated or not with E2. These results indicate that E2 exerts a direct action on PRL cells at the pituitary level and strongly support the key role of the hypothalamus in the inhibitory effect of androgens on estrogen‐induced stimulation of PRL mRNA in the male rat pituitary.
Simultaneous Display of Sexual and Ingestive Behaviour by Rats
Authors: Kaplan J. M. , Bednar I. , Södersten P. 
Published: September 2006

AbstractIntraoral infusion of sucrose activates consummatory ingestive behaviour in rats selectively, i.e. the rat only emits the responses used to ingest food. Activation of consummatory ingestive behaviour in this way had no effect on the subsequent display of sexual behaviour by male or female rats and vice versa. Rats infused intraorally with sucrose and presented with a sexual partner showed ingestive and sexual behaviour simultaneously. Pretreatment with cholecystokinin octapeptide inhibited the ingestion of sucrose in both males and females but had no effect on the simultaneous display of sexual behaviour. Ingestion of sucrose from a drinking spout, a test in which the rat has to emit responses to obtain food, i.e. show appetitive ingestive behaviour, was inhibited by the presentation of a sexual partner in rats of both sexes. These results show that the mechanisms controlling consummatory sexual and ingestive behaviour operate independently and that the presentation of a sexual partner inhibits appetitive ingestive behaviour.Daily intraoral infusion of sucrose reduced pellet intake in ovariectomized rats while the rats maintained their body weight. Implantation of an oestradiol‐filled implant reduced body weight and inhibited daily intake of pellets but had no effect on the intake of intraorally administered sucrose. Subsequent removal of the oestradiol implant increased sucrose intake and body weight but did not have a marked effect on pellet intake. Thus, rats respond to a lowering of the set point for body weight by decreasing their intake of the least preferable kind of food and increase their intake of the most preferable kind of food in response to an elevation of the set point for body weight. Ovariectomized rats infused intraorally once daily with a highly nutritive milk diet in the absence of food pellets ingested very large amounts and reduced their intake in response to oestradiol implantation. Thus, although oestradiol can inhibit consummatory ingestive behaviour, its suppressive effect on ingestion cannot be described in terms of selective effects on appetitive and/or consummatory aspects of the behaviour nor in terms of an alteration in the preference for a sweet solution.Inhibition of ingestive behaviour occurred within 24 h after oestrogen treatment as opposed to stimulation of sexual behaviour which had a longer latency, suggesting that oestradiol affects ingestive and sexual behaviour via different mechanisms. While the mechanisms controlling consummatory ingestive and sexual behaviour must be different, there is evidence for a common mechanism mediating the incentive motivation and reward aspects of these behaviours. The mechanisms which enable rats to select between two, possibly equally rewarding courses of action, i.e. display of sexual or ingestive responses, however, are unknown.
Steroid Regulation and Sex Differences in [3H]Muscimol Binding in Hippocampus, Hypothalamus and Midbrain in Rats
Authors: McCarthy M. M. , Coirini H. , Schumacher M. , Johnson A. E. , Pfaff D. W. , Schwartz‐Giblin S. , McEwen B. S. 
Published: September 2006

AbstractThe gonadal steroids estradiol and progesterone have previously been shown to modulate the specific binding of the GABAA agonist, [3H]muscimol, in the CA1 region of the hippocampus, the ventromedial nucleus of the hypothalamus and the midbrain central gray of ovariectomized female rats. In this report we show a sex difference in the level of binding in the very caudal ventromedial nucleus of the hypothalamus. In contrast to females, there is no steroid modulation of [3H]muscimol binding in the ventromedial nucleus of the hypothalamus and midbrain central gray of males. These effects may be functionally related to GABAergic control of female sexual behavior. In contrast, steroid modulation of [3H]muscimol binding in the CA1 region of the hippocampus occurred to the same degree in males and females, and there was no difference in the level of binding in any region of the hippocampus between gonadectomized males and females.Incubation of brain slices with progesterone or its metabolite 5α‐3α‐pregnanolone dissolved in ethanol, produced a significant increase in [3H]muscimol binding in most brain regions as compared to control brain slices treated with ethanol alone. Moreover, there was also a marked increase in [3H]muscimol binding in all brain areas in the control condition which contained 100 mM ethanol, as compared to brain slices not preincubated with ethanol. The increase in binding after in vitro treatment with either progesterone or 5α‐3α‐pregnanolone is notably different from that seen after progesterone given in vivo 4 h prior to assay in that it is not site‐specific, does not depend on prior treatment with estradiol and shows no sex difference. These results suggest different mechanisms for progesterone effects on the GABAA receptor when administered in vivo as compared to in vitro.
Reproductive History Affects the Synaptology of the Ageing Gonadotropin‐Releasing Hormone System in the Male Rat
Authors: Witkin Joan W. 
Published: September 2006

AbstractThis study is an examination of the density of synaptic input to gonadotropin‐releasing hormone (GnRH) neurons in young adult and aged retired breeder male rats. In earlier experiments on aged virgin male rats we observed an increase in synaptic input to this specific neuronal population, ascribable in part to synapses containing flattened vesicles, suggesting GABAergic input. The present study utilized retired breeders in order to dissect the effects of ageing from those associated with reproductive behavioral history. Tissue from the preoptic area was treated for the simultaneous electron microscopic immunocytochemical demonstration of GnRH with tetramethylbenzidine and glutamic acid decarboxylase (the essential enzyme in the production of GABA) using 3,3′‐diaminobenzidine. Estimates of the density of synaptic input to the soma of GnRH neurons were made by calculating the percentage of perikaryal membrane with postsynaptic modification. Five GnRH neurons per animal were measured using computerized morpho‐metrics and differences in the percent of membrane with synaptic modification between experimental groups were tested using the Mann‐Whitney U non‐parametric statistic. There was no difference in the total density of synaptic input to GnRH neurons in the young and old animals, or in the proportion of this input that was immunoreactive for glutamic acid decarboxylase. Similar measurements were made on random, non‐identified neurons in the same region and a significant decrease with ageing in total synaptic input was found, though the glutamic acid decarboxylase component was unchanged. The present results are in contrast to our earlier findings on virgin males and suggest that reproductive behavioral experience affects the connectivity of GnRH neurons.
Brain Angiotensin II Receptor Subtypes and the Control of Luteinizing Hormone and Prolactin Secretion in Female Rats
Authors: Stephenson K. N. , Steele M. K. 
Published: September 2006

AbstractThe present experiments examined the role of the two recently identified angiotensin II (Ang II) receptor subtypes, AT, and AT2, in the central nervous system regulation of luteinizing hormone (LH) and prolactin secretion in estrogen‐ and progesterone‐treated ovariectomized rats. In this animal model, intracerebroventricular (icv) injection of Ang II stimulates LH and inhibits prolactin release. The specific Ang II receptor subtype antagonists losartan (AT1) or PD123177 (AT2) were administered (icv) in various doses (10 ng to 1,000 ng) 10 min prior to icv injection of Ang II (100 ng). Control animals were pretreated with artificial cerebrospinal fluid prior to Ang II administration. Blood samples for LH and prolactin determinations were taken from conscious, freely‐moving rats prior to and following injection of the antagonists and Ang II. Water intake was measured.Ang ll‐induced water intake was attenuated 62% by 1,000 ng losartan; water intake was not affected by lower doses of losartan or by any dose of PD123177. Ang ll‐induced stimulation of LH release was abolished by the 1,000 ng doses of losartan and PD123177 and attenuated by the 500 ng doses of both drugs. Lower doses did not affect Ang ll‐induced LH secretion. Ang ll‐induced inhibition of prolactin release was significantly reduced by the 1,000 ng doses of both losartan and PD123177. Lower doses of either drug did not affect the Ang II inhibition of prolactin release.Previous studies had shown that Ang II administration into the anterior hypothalamus‐medial preoptic (AHPO) area stimulated LH release. This brain area contains AT1 receptors. To investigate the potential brain site where the AT2 receptor may influence LH release, Ang II was injected into the locus ceruleus, a brain nucleus which contains predominately the AT2 receptor subtype. Ang II administration into the locus ceruleus was paired with an injection of artificial cerebrospinal fluid or Ang II into the AHPO area.Injection of Ang II into the AHPO area stimulated LH release. Injection into the locus ceruleus did not affect LH secretion, nor did it modify the rise in LH elicited by administration of Ang II into the AHPO area. Plasma levels of prolactin were not altered by any of these injections.Taken together, these data demonstrate that, in estrogen‐ and progesterone‐treated female rats, icv Ang ll‐induced water intake is mediated by the AT, receptor subtype, while Ang ll‐induced changes in LH and prolactin secretion appear to be mediated by both the AT2 and AT2 receptor subtypes. The latter observations are one of the first suggesting a potential function for the AT2 subtype in vivo, although the physiological relevance of this observation, as well as the site of action for the effects on LH and prolactin, remain to be established.
Dopaminergic Regulation of Galanin Gene Expression in the Rat Anterior Pituitary Gland
Authors: Hyde James F. , Keller Brian K. , Howard Georgette 
Published: September 2006

AbstractEstrogen dramatically increases galanin mRNA and peptide levels in the rat anterior pituitary gland. We recently reported that galanin secretion in vitro from estrogen‐exposed anterior pituitary cells is regulated by hypothalamic factors; dopamine and somatostatin inhibit galanin secretion, and thyrotrophin‐releasing hormone stimulates galanin release. To determine whether galanin is regulated by a dopaminergic mechanism in vivo, we used ovariectomized Fischer 344 rats treated with 17ß‐estradiol‐containing or empty Silastic capsules. Rats were also administered bromocriptine, a dopamine receptor agonist, haloperidol, a dopamine receptor antagonist, or placebo for 2 weeks. Galanin peptide levels were measured in the anterior pituitary, neurointermediate lobe, medial basal hypothalamus, and plasma by radioimmunoassay. Plasma and pituitary prolactin levels were also determined. Bromocriptine decreased gaianin peptide levels in the anterior pituitary gland of ovariectomized rats by 30%, but had no effect on galanin in the neurointermediate lobe or medial basal hypothalamus. In contrast, haloperidol had no effect on galanin in the anterior pituitary or medial basal hypothalamus of ovariectomized rats, but decreased galanin peptide levels in the neurointermediate lobe. In the anterior pituitary gland of estrogen‐treated rats, bromocriptine increased and haloperidol decreased both galanin and prolactin levels. Galanin mRNA levels were quantified in the anterior pituitary gland by solution hybridization. Bromocriptine increased galanin mRNA levels 3‐fold in the anterior pituitary, whereas haloperidol had no effect. Galanin mRNA levels in the anterior pituitary were elevated 10‐fold by estrogen. Bromocriptine reduced galanin mRNA levels in the pituitary by 50% in estrogen‐treated rats, where again haloperidol had no effect. Estrogen increased plasma galanin levels 4‐fold compared to ovariectomized rats and this effect was reduced 60% by bromocriptine and increased 20% by haloperidol.We conclude 1) galanin synthesis and release from the estrogen‐exposed anterior pituitary gland is inhibited by a dopaminergic mechanism in vivo, 2) dopamine regulates galanin gene expression in the ovariectomized rat, 3) the changes in galanin peptide levels in the anterior pituitary of rats treated with estrogen and dopamine receptor ligands are primarily due to alterations in peptide secretion, and 4) galanin release from the neurointermediate lobe may also be regulated by a dopaminergic mechanism in vivo. These data, in conjunction with previous studies, provide evidence for the co‐regulation of galanin and prolactin in estrogen‐treated rats, and further discriminate between the regulation of galanin in the hypothalamus and pituitary gland.
Central Amygdaloid Involvement in Neuroendocrine Correlates of Conditioned Stress Responses
Authors: Roozendaal B. , Koolhaas J. M. , Bohus B. 
Published: September 2006

AbstractThe purpose of this study was to examine the effects of bilateral electrolytic lesions of the central nucleus of the amygdala (CEA) in comparison with sham lesions on neuroendocrine responses during conditioned emotional stress in male Wistar rats. Lesions in the CEA, made either before or after the single learning trial of inescapable footshock, failed to affect the conditioned response of plasma epinephrine levels. Plasma levels of norepinephrine showed neither a conditioned stress effect nor were influenced by lesioning. Pre‐training CEA lesions, but not post‐training intervention, abolished the conditioned elevations of circulating plasma corticosterone and prolactin. These results suggest that the CEA is involved in the conditioning rather than the retention of neuroendocrine stress responses. The effects of pre‐training lesioning of the CEA can possibly be explained by a reduced feedback of all these neuroendocrine factors during or shortly after acquisition. In addition, there is a remarkable differentiation between various hormonal correlates of conditioned stress following CEA lesioning. Only corticosterone and prolactin, that appear to be correlates of a passive behavioural stress response, were abolished. The lesions failed to affect the sympatho‐active stress parameters (epinephrine and norepinephrine). Relations between coping strategy—active and passive behaviour—and physiology in connection with CEA functioning are discussed.
The Chicken Vasotocin Gene
Authors: Hamann Danja , Hunt Nicholas , Ivell Richard 
Published: September 2006

AbstractcDNA clones corresponding to the vasotocin precursor polypeptide were isolated from a chicken hypothalamic library and sequenced. The derived amino‐acid sequence indicates a precursor of comparable structural organization to that described for members of the vasotocin/vasopressin gene family from other species. Unlike in mammals the C‐terminal glycopeptide moiety appears not be cleaved off from the neurophysin. Subsequent screening of a chicken genomic library permitted an analysis also of the vasotocin gene structure and exonic composition. The 5’region upstream of the first exon was sequenced and revealed an unusual pattern of 49 repetitive ‐YYCYCYAAAYY‐ motifs, together with a polyadenyl region supporting a bend in the DNA, and a long pyrimidine‐rich sequence. Three AP2‐like elements, identified in the mammalian vasopressin gene, were also observed in the immediate upstream region. There was no obvious homology to the promoter regions of the known oxytocin genes, nor to any other sequence deposited in available databases, nor to other known cis‐elements.