bluuebunny/crossref_metadata_2025 huggingface dataset:
Centrally Injected lnterleukin‐1 Beta Inhibits the Hypothalamic LHRH Secretion and Circulating LH Levels via Prostaglandins in Rats
Authors: Rivest Serge , Rivier Catherine
Published: September 2006

Intracerebroventricular (icv) infusion of interleukin‐1ß (IL‐1ß) significantly lowers plasma LH levels in castrated male rats, and interferes with LHRH release into the median eminence of proestrus female rats. We have investigated the potential role of arachidonic acid metabolites in mediating these inhibitory effects, by administering indomethacin (INDO, a cyclooxygenase inhibitor) or nor‐ dihydroguaiaretic acid (NDGA, a lipoxygenase inhibitor) 15 min prior to injection of the cytokine. While not measurably altering basal LH or LHRH secretion in castrated or proestrus rats, respectively, INDO completely reversed the action of IL‐1ß on the secretion of these 2 hormones. In contrast, NDGA did not alter IL‐1‐induced decreases in LH release.

The peripheral administration of endotoxin (LPS) also interferes with LH release. Because the iv injection of IL‐1 does not alter LH secretion, this effect is believed to be at least in part mediated by increased synthesis of cytokines within the CNS. We observed that in contrast to results obtained in rats injected with IL‐1 icv, INDO did not reverse the inhibitory action of LPS. Our results thus suggest either that central IL‐1 is not the primary modulator of LPS‐induced decrease in LH values, or that pathways other than those involving arachidonic acid are important.

In conclusion, we have shown that: 1) the ability of IL‐1ß to decrease the activity of the HPG axis is dependent on arachidonic acid metabolites (in particular those formed through the eicosanoid cyclooxygenase route); 2) under circumstances of increased IL‐1ß levels within the CNS, prostaglandins exert an overall inhibitory effect on the hypothalamic LHRH secretion and plasma LH levels in rats.
A Functional Promoter Directing Expression of a Novel Type of Rat Mineralocorticoid Receptor mRNA in Brain
Authors: Castrén Maija , Damm Klaus
Published: September 2006

The authors have identified two types of hippocampal cDNAs for the rat mineralocorticoid receptor (rMR) which are identical in the protein coding domain but differ in their 5′‐untranslated sequences. One of these clones encodes a novel type of rMR cDNA with a high homology to a previously described human MR cDNA isolated from the kidney. A genomic clone containing the 5′‐end of the rat MR gene was isolated. The 12.7 kb genomic region contains the 5′‐coding exon with the translational start site and contiguous DNA sequences encoding the N‐terminal domain of the rMR. A 240 bp region homologous to the 5′‐untranslated sequences of the novel rMR cDNA was located 5.2 kb upstream the protein coding region. Characterization of the nucleotide sequence preceding this exon revealed several features characteristic for promoters of so‐called ‘housekeeping genes'. The sequence analyzed is 635 bp in length, is rich in G + C nucleotides (63%) and lacks TATA or CAAT regulatory elements. It contains three putative binding sites for transcription factor Sp1 as well as several short sequences that are similar to known cis‐acting enhancers or binding sites for transcription factors. In transient transfection experiments employing the luciferase reporter gene and the CV1 cell line this region exhibits substantial promoter activity. These experiments demonstrate that expression of the rat MR gene in the hippocampus results in at least two transcripts with different 5′‐untranslated exons. This sequence information together with the nucleotide sequences upstream of one of the exons, which were shown to encode a functional promoter, provide a valuable tool to elucidate the mechanisms involved in the tissue‐specific regulation of the rat MR gene.
Depolarizing Action of Secretory Granule Protein 7B2 on Rat Supraoptic Neurosecretory Neurons
Authors: Senatorov Vladimir V. , Yang Charles R. , Marcinkiewicz Mieczyslaw , Chrétien Michel , Renaud Leo P.
Published: September 2006

A novel precursor neuropeptide termed 7B2 is present within specific brain areas, including the hypothalamic magnocellular neurosecretory neurons, and appears to be processed to smaller fragments. In order to determine whether specific C‐terminal fragments of 7B2 might exert local effects on neurosecretory cells, we used intracellular current‐clamp recordings in supraoptic neurons maintained in superfused hypothalamic explants to evaluate membrane potential and resistance changes in 25 supraoptic nucleus neurons during bolus applications of 7B2174–186 and two other C‐terminal peptide fragments 7B2156–173 and 7B2141–150. In 15 supraoptic neurons, only the 7B2174–186 fragment induced a gradual 2–8 mV membrane depolarization that lasted for 4 to 30 min and was accompanied by 15 + 8% reduction in input resistance. Immunocytochemical identification of the recorded cells revealed that both vasopressin (VP)‐ and oxytocin (OT)‐containing neurons were depolarized by 7B2174–186. These data suggest that 7B2174–186 is a biologically active fragment of 7B2 and may regulate the excitability of magnocellular supraoptic nucleus neurons.
Decreased Population Spike in CA1 Hippocampal Area of Adrenalectomized Rats after Repeated Synaptic Stimulation
Authors: Joëls M. , Fernhout B.
Published: September 2006

Population spikes, evoked in the CA1 hippocampal area by stimulation of the Schaffer collaterals at various intensities, were recorded over a period of 70 min in slices from 7‐day adrenalectomized (ADX) or sham‐operated rats. Slices from sham‐operated rats with intermediate plasma corticosterone levels (between 0.5 and 5μg corticosterone/100 ml plasma) at the start of the experiment displayed very stable synaptic responses. However, the responses recorded in slices from rats with lower or higher corticosterone levels gradually declined, with repeated stimulation. Similarly, a significant decline of the population spike over time was observed in slices from ADX rats, particularly with low stimulus intensities; characteristics of the compound EPSP were much more stable. The decline of the population spike amplitude was alleviated when: 1) single rather than repeated stimulation was applied; 2) the experiments were performed in the presence of 20 mM glucose; or, 3) moderately high (10−8 or 10−7 M) concentrations of corticosterone were administered in vitro; low (10−9 M) or high (10−6 M) corticosterone concentrations in vitro did not improve the stability of the synaptic response in slices from ADX rats. These data suggest that intermediate levels of corticosterone are necessary to maintain the stability of the Schaffer collateral input to CA1 neurons. With very low or high corticosterone levels, CA1 neurons apparently fail to respond to synaptic stimulation, over time. The possible mechanisms underlying this bell‐shaped dose response curve for corticosterone are discussed.
Formation of Neurons in the Sexually Dimorphic Anteroventral Periventricular Nucleus of the Preoptic Area of the Rat: Effects of Prenatal Treatment with Testosterone Propionate
Authors: Nishizuka Masako , Sumida Hiroyuki , Kano Yasuhiko , Aral Yasumasa
Published: September 2006

An examination was made of neurogenesis in the anteroventral periventricular nucleus (AVPv) of the preoptic area of the rat using bromodeoxyuridine (BrdU), a thymidine analog, and a BrdU‐specific antibody. Cells in the AVPv of adult rats were labeled with the antibody when BrdU was injected into pregnant rats once during day 13 to 18 of gestation, but not during day 10 to 12 nor 19 to 20 of gestation nor on postnatal day 1, indicating that neurogenesis of the AVPv occurs during a limited period from day 13 to 18 of gestation. Next, to examine the effects of androgen on neurogenesis, BrdU was injected once on day 15 into pregnant rats that also received injections of testosterone propionate (TP). The number of BrdU‐labeled cells in the AVPv was similar in control female and male fetuses and female fetuses from pregnant rats that received daily injections of TP during days 14 to 16, when fetuses were examined on day 17 of gestation. These results suggest that the neurogenesis that was recognized by labeling with BrdU was not affected by the treatment with TP. On day 21 of gestation, BrdU‐labeled cells in the AVPv of control male fetuses and female fetuses that received TP during days 14 to 18 were fewer in number than those in female fetuses of the control group, whereas treatments with TP during days 14 to 16 and during days 17 to 18 did not cause any significant decrease in number of BrdU‐labeled cells. These findings support the hypothesis that elimination of a population of cells, for example, by cell death as described previously, is enhanced in male fetuses and in female fetuses treated with TP repetitively.
P‐chlorophenylallanine Facilitates Copulatory Behavior in Septal Lesioned but not in Preoptic Lesioned Male Rats
Authors: Kondo Yasuhiko , Yamanouchi Korehito , Arai Yasumasa
Published: September 2006

Effects of p‐chlorophenylalanine (pCPA), synthesis‐inhibitor of serotonin, on copulatory behavior were examined in testosterone (T) treated castrated male rats with lesions in the lateral septum (LSL) or in the medial preoptic area (MPOL). Three weeks after the operation, all animals were chronically treated with T using silastic capsules. Behavioral tests were carried out at 10 and 20 days after the implantation of T. In half of the males in each group, 100 mg/Kg pCPA was injected daily for 4 days before each test. The other half of the group was injected with saline instead of pCPA. In saline‐treated groups, the males with LSL or MPOL showed extremely lower frequencies of mount and intromission than control males without brain surgery. PCPA‐treated control males showed higher copulatory activities than saline‐treated control males. In contrast, even after the treatment with pCPA, severe impairment of sexual behavior was observed in males with MPOL. On the other hand, pCPA‐treated LSL males displayed copulatory behavior more frequently than saline‐treated LSL males. These results agreed with previous reports that both the medial preoptic area and the lateral septum play an excitatory role in regulating male sexual behavior. Conversely, the serotonergic neuronal system exerts an inhibitory influence for male sexual behavior. Furthermore, these results suggest that the inhibitory function of serotonergic neurons govern dependently on the function of the medial preoptic area, but independently on the function of the lateral septum.
Secretogranin II: Regulation of Synthesis and Post‐Translational Proteolysis in Bovine Adrenal Chromaffin Cells
Authors: Soszynski Darek , Metz‐Boutigue Marie‐Hélène , Aunis Dominique , Bader Marie‐France
Published: September 2006

Secretogranin M (Sgll), also called chromogranin C, is an acidic tyrosine‐sulfated secretory protein found in secretory granules in a wide variety of endocrine cells and neurones. Although less abundant than chromogranin A (CGA) and chromogranin B (CGB), Sgll is found in adrenal medullary chromaffin granules. In the present study we investigated the regulation of Sgll biosynthesis in bovine chromaffin cells maintained in primary culture. Cellular proteins were labelled with [35S]methionine and the heat stable chromogranin enriched fraction was isolated. Following electrophoretic separation, the 86 kDa Sgll band was identified by sequence analysis using the Edman degradation procedure. The radioactivity incorporated in the 86 kDa Sgll band was used as an index of the Sgll synthesis rate. We found that stimulation of chromaffin cells with nicotine and histamine and to a smaller extent with angiotensin II and bradykinin significantly enhanced the rate of Sgll synthesis. In contrast direct depolarization with K+ had no effect on Sgll synthesis suggesting that the raise of cytosolic calcium evoked by high K+ may not be sufficient to induce modifications in Sgll synthesis. The possible second messenger pathways involved in the control of Sgll biosynthesis were investigated by using protein kinase C and adenylate cyclase activators. We observed that 12‐O‐tetradecanoylphorbol 13‐acetate (TPA) and forskolin increased the basal rate of Sgll synthesis. Incubation with both TPA and forskolin was required to obtain an effect comparable to that produced by nicotine or histamine suggesting that these secretagogues recruit both protein kinase C‐ and cyclic AMP‐dependent mechanisms to stimulate Sgll synthesis. Our results indicate that within chromaffin granules, the rates of CGA, CGB and Sgll synthesis are independently regulated and suggest a close relationship between the cell secretory activity and the biosynthesis of Sgll.

The biological role of Sgll is unknown but it has been suggested that the protein may function as a precursor of potentially bioactive peptides. Here we identified a Sgll derived peptide corresponding to the C‐terminal residues 582–586 in the soluble core of purified chromaffin granules. This peptide was released together with catecholamines upon stimulation of cultured chromaffin cells indicating that the peptide was present within the storage complex of chromaffin granules and was not the result of some artefactual proteolytic degradation of Sgll during the course of granule purification. We propose that this peptide is a specific product of the post‐translational processing of Sgll. By analogy with peptides derived from CGA and CGB, it may possess some specific biological activity that remains to be identified.
Regulation of Cholecystokinin Receptors in the Hypothalamus of the Rat: Reciprocal Changes in Magnocellular Nuclei Induced by Food Deprivation and Dehydration
Authors: O'Shea Ross D. , Gundlach Andrew L.
Published: September 2006

Cholecystokinin (CCK) has been suggested to mediate satiety in a number of non‐primate species via its peripheral actions as well as a possible central mechanism involving magnocellular and parvocellular oxytocin release. Quantitative in vitro autoradiography employing [125l]‐Bolton‐Hunter labelled CCK‐8S ([125I]‐CCK‐8S) was used to examine the distribution and density of CCK receptors in sections of brain from normal rats and rats deprived of food, water or both food and water for 4 days. In food‐deprived rats, specific [125I]‐CCK‐8S binding was reduced by 64 ± 5% in the hypothalamic supraoptic nucleus (SON) and by 44±13% in the paraventricular nucleus of the hypothalamus (PVN). In contrast, water deprivation increased binding of [125I]‐CCK‐8S by 128±15% in the SON and by 196 ± 24% in the PVN, while combined food and water deprivation produced smaller increases in both nuclei (30 ± 5% and 98 ± 26% in SON and PVN respectively). Changes in receptor density in the PVN appeared to be most prominent in the magnocellular (especially oxytocin‐rich) subdivisions. None of the treatments employed produced changes in [125I]‐CCK‐8S binding in the ventromedial hypothalamic nucleus or the reticular thalamic nucleus. Both CCK‐A and CCK‐B receptor subtypes were visualized in the nucleus of the solitary tract and the area postrema of normal rats, but levels of binding to both of these subtypes were unaffected by the experimental treatments. These selective alterations demonstrate the plasticity of CCK receptors in the SON and PVN, and are probably associated with changes in the level of neurochemical activity of magnocellular oxytocinergic neurones in these areas. These results, together with reports of changes in the level of CCK synthesis in cells of the SON and PVN after hyperosmotic stimuli, suggest that CCK may act in an autocrine fashion on these neurones and that both CCK receptors and peptide levels are altered in the same direction following cellular activation or inhibition.
Changes in Pro‐Opiomelanocortin and Pre‐proenkephalin mRNA Levels in the Ovine Brain during Pregnancy, Parturition and Lactation and in Response to Oestrogen and Progesterone
Authors: Broad K. D. , Kendrick K. M. , Sirinathsinghji D. J. S. , Keverne E. B.
Published: September 2006

In the female sheep opioids act centrally to influence both oxytocin release and maternal behaviour. We have used in situ hybridization histochemistry to investigate the changes in mRNA expression of the two opioid precursor genes, proopiomelanocortin (POMC) and pre‐proenkephalin (PPE), in discrete hypothalamic nuclei as a function of pregnancy, parturition and lactation and following treatment with oestrogen and progesterone. Quantitative in situ hybridization histochemistry demonstrated that POMC mRNA expression in the arcuate nucleus (ARC) decreased at parturition and increased during lactation compared to late pregnant and ovariectomized animals. Oestradiol and progesterone treatments increased POMC mRNA expression compared to ovariectomized controls. Pre‐proenkephalin mRNA expression was quantified in three discrete hypothalamic nuclei, the ventromedial nucleus (VMN), the paraventricular nucleus (PVN) and the suprachiasmatic nucleus (SCN). In the VMN, PPE mRNA expression increased during lactation compared to late pregnancy and parturition. Expression levels during late pregnancy and parturition were decreased compared to ovariectomized animals. Oestradiol increased, and progesterone decreased, PPE mRNA levels compared to ovariectomized controls. Combined progesterone followed by oestrogen treatment produced significant increases in PPE mRNA expression. In the PVN, PPE expression increased at parturition compared to late pregnant, lactating and ovariectomized animals. Expression levels in late pregnant animals were decreased compared to lactating or ovariectomized ones. However, sex steroid treatment produced no changes in PPE expression in the PVN. No changes were observed in PPE mRNA expression in the SCN in response to any of the experimental conditions. This data shows that both POMC and PPE mRNA levels are altered in the sheep brain during pregnancy, parturition and lactation and in response to sex steroids, although the direction of the changes is not always the same and in the case of PPE only the VMN and PVN are affected. Levels of gene expression found following exogenous steroid treatment do not precisely mirror those found during pregnancy, parturition and lactation and this suggests that factors other than changing sex steroids levels are involved. In the context of maternal behaviour it is interesting to note that PPE mRNA expression increases at parturition in the PVN when oxytocin mRNA expression levels are also increased.
Rapid Changes in Somatostatin and TRH mRNA in Whole Rat Hypothalamus in Response to Acute Cold Exposure
Authors: Rage Florence , Lazaro Jean‐Bernard , Benyassi Ahmed , Arancibia Sandor , Tapia‐Arancibia Lucia
Published: September 2006

Acute cold stimulus induces activation of the thyreotropic axis characterized by a rapid increase in plasma thyrotropin (TSH). Since pituitary TSH release is mainly regulated by two hypothalamic hormones: thyrotropin‐releasing hormone (TRH) and somatostatin, the aim of this study was to analyse whether changes in the steady state mRNA levels and peptide content of these neurohormones occur under acute cold stimulation in rats. Northern blot analysis of hypothalamic somatostatin mRNA levels after 15, 30, 60 or 180 min of cold exposure revealed a 2.0‐fold increase after 15 min at 4°C. This augmentation was followed by a return to control values at 30 min. However, the hypothalamic content of somatostatin was not significantly modified at any cold exposure time. TRH mRNA showed a similar pattern to somatostatin, with a 2.5‐fold increase after 15 min at 4°C. In contrast, hypothalamic TRH content was significantly decreased after 15 min cold exposure, returning to control values at 30 min. The increase in mRNA levels was specific for the two hypothalamic hormones, since there was no concomitant variation in GAPDH mRNA used as negative control. These results suggest that the organism is quickly aroused by cold stimulus, triggering rapid activation in transcription of the two neurohormones involved in the regulation of the thyreotrope axis. Since the peptide contents did not show the same pattern, a quantitative change in transcription or in mRNA stability does not appear to be a prerequisite for increased peptide expression, suggesting that somatostatin and TRH gene expressions could be regulated at translational or post‐translational steps.
Effect of Late Hypothalamo‐Pituitary Disconnection on the Development of the HPA Axis in the Ovine Fetus and the Initiation of Parturition
Authors: Deayton Jan M. , Young I. Ross , Hollingworth Samantha A. , White Anne , Crosby Steve R. , Thorburn Geoffrey D.
Published: September 2006

The studies of Liggins et al. (1) in which fetuses stalk‐sectioned from day 116 onwards delivered at or near term, suggested that a connection between the fetal hypothalamus and pituitary is not essential for parturition to occur. The objective of this study was to repeat these experiments on the effects of pituitary stalk sections at different gestational ages and include information on the plasma concentrations of key fetal hormones. We have used the more sophisticated technique of hypothalamo‐pituitary disconnection (HPD) at either of two gestational age ranges (123–127 days or 133–135 days). Completeness of the procedure was assessed by demonstrating an attenuated prolactin response to chlorpromazine challenge. Following HPD, gestation was prolonged for at least eight days beyond term (146.2 ± 1.5 days) in 9 of the 10 fetuses operated. Fetal plasma ACTH1–39 concentrations were not different between the HPD and control fetuses, increasing in all groups with increasing gestation. Fetal plasma cortisol concentrations increased (P<0.01) in control fetuses over gestation. Cortisol concentrations did not change significantly in the day 125 HPD group following HPD but increased in the day 135 HPD group (P<0.05) with advancing gestation. These latter concentrations, however were markedly less (P< 0.001) than those for control fetuses prior to parturition. Fetal and maternal plasma PGE2 concentrations increased (P<0.01) in the control group over gestation but did not change following HPD. Maternal plasma progesterone concentrations decreased (P<0.05) after day 143 in the control group but did not change in the HPD group. There was no change in maternal plasma concentrations of prostaglandin FM in the HPD group. These findings demonstrate that hypothalamic connection to the pituitary needs to be maintained until at least day 135 of gestation for the initiation of parturition at term.
Chronic Administration of Glucocorticoids Directly Upregulates Prepro‐Neuropeptide Y and Y1‐Receptor mRNA Levels in the Arcuate Nucleus of the Rat
Authors: Larsen Philip J. , Jessop David S. , Chowdrey Hardial S. , Lightman Stafford L. , Mikkelsen Jens D.
Published: September 2006

The complete sequence of the cDNA encoding the neuropeptide Y (NPY) Y1‐receptor has recently been deduced from a rat brain library, and the presence of messenger ribonucleic acid (mRNA) encoding Y1‐receptor protein has been demonstrated within the brain. Using quantitative in situ hybridization histochemistry, the content and distribution of Y1receptor and preproNPY mRNAs have been investigated in the hypothalamic arcuate nucleus of adrenalectomized rats receiving glucocorticoid replacement therapy for 12 days by means of either high doses of dexamethasone in their drinking water or by subcutaneous corticosterone pellets. Basal metabolic parameters such as weight gain or loss, blood glucose and plasma insulin were monitored: Dexamethasone treatment induced weight loss and a state of hyperinsulinemia with normoglycemia, while corticosterone treated animals displayed metabolic parameters identical to sham ADX animals. Within the arcuate nucleus of glucocorticoid treated animals, levels of Y1receptor and preproNPY mRNAs were increased. In contrast, adrenalectomy itself had no effect upon Y1‐receptor mRNA levels or preproNPY mRNA levels in the arcuate nucleus. These studies demonstrate that glucocorticoids exert a stimulatory action on levels of Y1‐receptor mRNA and preproNPY mRNA levels in the hypothalamic arcuate nucleus. This is the first evidence to suggest that the expression of a neuropeptide‐receptor gene in the central nervous system may be directly sensitive to peripheral hormonal signals.
Effects in vitro of New Growth Hormone Releasing Peptide (GHRP‐1) on Growth Hormone Secretion from Ovine Pituitary Cells in Primary Culture
Authors: Wu Danxing , Chen Chen , Zhang Jin , Katoh Kazuo , Clarke Lain
Published: September 2006

Continuous perifusion of pituitary cells was used to study the effects of a newly synthesized GHRP (GHRP‐1 or KP 101) on growth hormone (GH) secretion from ovine pituitary cells and these have been compared to effects of growth hormone‐releasing factor (GRF) and the original growth hormone‐releasing peptide (GHRP‐6). GH was continuously released at a constant rate during perifusion and secretion was increased by KP 101, GHRP‐6 and GRF in a dose‐dependent manner. The half‐maximal effective dose of KP 101 and GHRP‐6 was 10−7 M, an order of magnitude higher than that for GRF. The maximal effects of KP 101 and GHRP‐6 were similar but significantly less than the maximal effect of GRF. Blockade of calcium channels with Cd2+ (2 mM) totally and reversibly abolished the releasing effects of all three peptides. Like GHRP‐6, the GH release induced by KP 101 was not affected by a GRF antagonist ([Ac‐Tyr1, D‐Arg2]‐GRF 1–29, 1 μM) which significantly reduced the effect of GRF on GH release. For each peptide, the response to a second application (1 h after the first application) was lower than the first response. When GRF (or KP 101, GHRP‐6) was applied first and then KP 101 or GHRP‐6 (or GRF) given 1 h later, the second response was not attenuated. Only a small additive effect on the release of GH by GRF was obtained by the co‐administration of either KP 101 or GHRP‐6. This result was achieved with maximal doses of the peptides, but not with half‐maximal doses. These data indicate that KP 101 has similar potency and GH releasing properties to GHRP‐6 but both are less potent than GRF. There is no synergistic effect of the peptides with GRF and only a small additive effect of KP 101 or GHRP‐6 on GRF‐stimulated GH release from ovine pituitary cells in vitro. KP 101 stimulates GH release by a mechanism that involves a common step employed also by GRF and GHRP‐6, an increase in calcium influx. In addition, our data strongly suggest that KP 101 like GHRP‐6 do not act through the GRF receptor and that there is no cross‐desensitization the GRF elicited response.
Prolactin Receptor mRNA Localization in the Hypothalamus by in situ Hybridization
Authors: Chiu Sufen , Wise Phyllis M.
Published: September 2006

Prolactin receptors may mediate the action of prolactin in the brain to influence behavior and neuroendocrine secretions. We recently demonstrated prolactin receptor gene expression in the anterior and medial basal hypothalamus and not in the cortex by the reverse transcription‐polymerase chain reaction. In this paper, we localize the prolactin receptor gene expression to individual cells with in situ hybridization. Several steps in the in situ hybridization method were modified to increase sensitivity by using (i) probes complementary to the coding sequence of the extracellular binding domain common to both long and short prolactin receptor, (ii) more stringent hybridization and wash conditions to reduce background and (iii) higher specific activity, more complex and saturating amounts of probe. We detected prolactin receptor gene expression in cells of the periventricular area of the preoptic nucleus, medial preoptic nucleus, supraoptic nucleus, rostral arcuate nucleus and choroid plexus. Cortical brain tissue, which has been demonstrated previously by reverse‐transcription polymerase chain reaction to be lacking in prolactin receptor mRNA, did not have any detectable signal for the receptor mRNA and was used as an indication of background levels of signal. The mean area of silver grains over labeled cells in periventricular area of the preoptic nucleus, medial preoptic nucleus, supraoptic nucleus, arcuate nucleus, lateral ventromedial nucleus was at least 10 times greater than the background in the cortex of the same brain section.
Proopiomelanocortin Gene Expression During Pig Pituitary and Brain Development
Authors: Ma E. , Milewski N. , Grossmann R. , IveII R. , Kato Y. , Ellendorff F.
Published: September 2006

The expression of proopiomelanocortin (POMC) mRNA, which plays an important role in neural, endocrine, neuroendocrine and immune systems, was studied by in situ hybridization during the development of pituitary in the domestic pig. The POMC gene was activated as early as fetal day 30 (E30). The signal for POMC mRNA in the anterior lobe progressively increased from E30 to E80 and then remained at relatively constant level. In contrast, POMC transcripts in the intermediate lobe first appeared at E40 and steadily increased during development. POMC transcripts in the brain were first found at E40 and were scattered in the arcuate nucleus (AN) and nucleus medialis thalami (NMT). At E50 the extra‐pituitary POMC mRNA was located not only in the AN and NMT but also in the fasciulus tegmenti and entorhinal cortex. In the posterior lobe, no signal was detected. The specific pattern of expression of the pig POMC gene in the pituitary and in specific regions of the central nervous system suggests important roles for POMC in fetal development. These results also suggest that POMC is excellent for studying the expression and regulation of pituitary hormone genes because of its tissue‐specific regulation and developmental pattern.
Intraneuronal Convergence of Tactile and Hormonal Stimuli Associated with Female Reproduction in Rats
Authors: Tetel Marc J. , Celentano Diane C. , Blaustein Jeffrey D.
Published: September 2006

Stimulation of the vagina and cervix, by mating or manual probing, elicits many behavioral and endocrine changes associated with female reproduction in rats. We and others have identified neurons in the medial preoptic area, medial division of the bed nucleus of the stria terminalis, posterodorsal portion of the medial amygdala, ventromedial hypothalamus, dorsomedial hypothalamus and midbrain central gray that increase Fos expression in response to vaginal‐cervical stimulation (VCS). In the present study, we used a double‐label immunofluorescent technique to determine if any of these VCS‐responsive neurons also contained estrogen receptor‐immunoreactivity. We found that over 80% of the VCS‐induced Fos‐IR neurons in the medial division of the bed nucleus of the stria terminalis also contained estrogen receptor‐immunoreactivity. Furthermore, high percentages of VCS‐responsive neurons in the medial preoptic area, posterodorsal medial amygdala, ventromedial hypothalamus and midbrain central gray contained estrogen receptor‐immunoreactivity as well. These results suggest that sensory and hormonal information associated with female reproduction converge on specific populations of neurons and may be integrated at the molecular level within these neurons.
Hypophysiotropic Role and Hypothalamic Gene Expression of Corticotropin‐Releasing Factor and Vasopressin in Rats Injected with Interleukin‐1β Systemically or into the Brain Ventricles
Authors: Lee Soon , Rivier Catherine
Published: September 2006

Intact adult male rats were injected intravenously (i.v., 400 ng/kg), intraperitoneally (i.p., 400 ng/kg) or intracerebroventricularly (i.c.v., 100 ng/kg) with interleukin‐1β (IL‐1β) or its vehicle. In comparison with vehicle‐treated animals, IL‐1β induced significant (P<0.01) increases in plasma ACTH levels measured 30 min later regardless of the route of cytokine administration. These changes were markedly blunted in rats administered specific antibodies directed against corticotropin‐releasing factor (CRF). In contrast, vasopressin (VP) antibodies significantly blunted ACTH released by the i.c.v. injection of IL‐1β, but only modestly altered the effect of the systemic injection of the cytokine. We then used semi‐quantitative in situ hybridization analysis to measure changes in steady‐state mRNA levels, as they might occur in response to these same doses of IL‐1β. Following administration of the vehicle, measurement of gene expression in the paraventricular (PVN) portion of the hypothalamus indicated a measurable amount of hybridization signals for both CRF and VP. No detectable changes in either CRF or VP gene expression were observed in rats injected with IL‐1β i.v. or i.p. 5 h earlier. In contrast, the i.c.v. administration of the cytokine significantly (P<0.01) increased both CRF and VP mRNA levels measured 5 h later.

These results suggest that while endogenous CRF modulates the response of the corticotrophs to this cytokine regardless of the route of administration, the role of VP is more important in rats injected centrally than in those injected peripherally. The observation that at the dose tested and over the time‐course studied, systemic injection of IL‐1β failed to alter CRF or VP gene expression, supports our earlier hypothesis that blood‐born IL‐1β acts primarily at the level of nerve terminals in the median eminence.
The Neuroendocrinology of the Adrenal Cortex
Authors: Vinson G. P. , Hinson J. P. , Tóth I. E.
Published: September 2006

Although until relatively recently assumed to be devoid of innervation, there is now ample proof that the adrenal cortex receives specific neurones of several types. A general interpretation of their roles in the regulation of adrenocortical function has not been forthcoming, probably because of the variety of the different experimental approaches which have been used, and the heterogeneous observations which have been made. We here summarize the evidence which is available, and offer the view that neural inputs may provide fine tuning of the responses to systemic factors such as ACTH, through direct actions on specific adrenocortical cells. However, neural regulation also provides an integrative function, through actions on the flow of blood through the gland, which itself exerts a powerful influence on adrenocortical function.
Glucocorticoids Regulate Hippocampal 11β‐Hydroxysteroid Dehydrogenase Activity and Gene Expression in vivo in the Rat
Authors: Low Susan C. , Moisan Marie‐Pierre , Noble June M. , Edwards Christopher R. W. , Seckl Jonathan R.
Published: September 2006

Chronic glucocorticoid excess or deficiency is associated with hippocampal dysfunction and neuronal death. 11β‐hydroxysteroid dehydro‐genase (11β‐OHSD), which catalyses the reversible conversion of corticosterone to inactive 11 ‐dehydrocorticosterone, regulates glucocorticoid access to receptors in the kidney and liver in vivo. The enzyme is also present in the hippocampus where it might modulate glucocorticoid action. We examined the effects of corticosteroid manipulations on hippocampal and peripheral 11β‐OHSD. In the hippocampus, chronic adrenalectomy (10 days) had no effect on 11β‐OHSD activity, compared to sham‐operated controls. Treatment of adrenalectomized animals with dexamethasone (200 μg/kg.day−1), but not aldosterone (20 μg/kg.day−1), for 10 days significantly increased hippocampal 11β‐OHSD activity compared with sham or adrenalectomized rats (22% and 23% rise respectively, P<0.05). These effects reflect changes in transcription of the liver‐type 11β‐OHSD gene, with dexamethasone significantly increasing 11β‐OHSD mRNA expression in the hippocampus compared with sham or adrenalectomized animals (32% and 70% higher respectively, P<0.05). In the liver, adrenalectomy significantly reduced 11β‐OHSD activity (16% lower), which was restored to sham levels by dexamethasone, but not aldosterone. Similar trends were seen in 11β‐OHSD mRNA expression, although these did not reach significance. None of the manipulations altered 11β‐OHSD activity or mRNA expression in the kidney. The hippocampal effects of dexamethasone were similar to those of chronic stress (arthritis) which increased 11β‐OHSD activity (20% rise, P<0.05), although this was not reflected at the level of mRNA. Thus, hippocampal (and hepatic, but not renal) 11β‐OHSD appears to be regulated by chronic glucocorticoid manipulations and stress. Hippocampal 11β‐OHSD may thus ensure optimal long‐term corticosterone exposure of glucocorticoid‐sensitive neurons.
Regulation of Pituitary Vasopressin Receptors during Chronic Stress: Relationship to Corticotroph Responsiveness
Authors: Aguilera Greti , Pham Quocan , Rabadan‐Diehl Cristina
Published: September 2006

The relationship between vasopressin (VP) receptor levels in the anterior pituitary and VP‐stimulated ACTH release in vitro was studied in rats subjected to various chronic stress paradigms. The stress models used were water deprivation for 60 h and administration of 2% NaCI in the drinking water (both of which are associated with decreased pituitary ACTH responsiveness), and repeated i.p.hypertonic saline injections or repeated daily immobilization for 14 days (associated with increased ACTH responsiveness to novel stimuli). VP receptors were measured by binding of [3H]arginine‐VP to anterior pituitary membrane‐rich fractions, and ACTH responses to VP in collagenase dispersed anterior pituitary cells. In control rats, binding of [3H]AVP was saturable and high affinity, with a Kd of 0.45 ± 0.05 nM and a Bmax of 138.8 ± 8.1 fmol/mg. In pituitary membranes from stressed rats, binding affinity was unchanged, but Bmax changed according to the type of stress. While VP binding was markedly reduced after water deprivation and 2% saline (25% and 49%, respectively), it was significantly increased after repeated i.p. hypertonic saline injections and repeated immobilization (126% and 154% of controls, respectively). The changes in VP binding were associated to parallel changes in maximum VP‐stimulated ACTH production in vitro, with a 34% decrease in water deprived rats and a 25% increase in hypertonic saline injected rats. The potentiating effect of VP on corticotropin releasing hormone‐stimulated ACTH was also reduced in cells from water‐restricted rats, and increased in cells from rats given repeated injections of hypertonic saline. The data show a direct relationship between changes in corticotroph responsiveness and changes in pituitary VP receptors during chronic stress, suggesting that pituitary VP receptor regulation is involved in the adaptation of the HPA axis during chronic stress.
Prenatal Stress Increases the Hypothalamo‐Pituitary‐Adrenal Axis Response in Young and Adult Rats
Authors: Henry Chantal , Kabbaj Mohamed , Simon Hervé , Le Moal Michel , Maccari Stefania
Published: September 2006

Prenatal stress is considered as an early epigenetic factor able to induce long‐lasting alterations in brain structures and functions. It is still unclear whether prenatal stress can induce long‐lasting modifications in the hypothalamo‐pituitary‐adrenal axis. To test this possibility the effects of restraint stress in pregnant rats during the third week of gestation were investigated in the functional properties of the hypothalamo‐pituitary‐adrenal axis and hippocampal type I and type II corticosteroid receptors in the male offspring at 3, 21 and 90 days of age. Plasma corticosterone was significantly elevated in prenatally‐stressed rats at 3 and 21 days after exposure to novelty. At 90 days of age, prenatally‐stressed rats showed a longer duration of corticosterone secretion after exposure to novelty. No change was observed for type I and type II receptor densities 3 days after birth, but both receptor subtypes were decreased in the hippocampus of prenatally‐stressed offspring at 21 and 90 days of life. These findings suggest that prenatal stress produces long term changes in the hypothalamo‐pituitary‐adrenal axis in the offspring.
Simultaneous Monitoring of Intracerebral Release and Behavior: Endogenous Vasopressin Improves Social Recognition
Authors: Engelmann Mario , Ludwig Mike , Landgraf Rainer
Published: September 2006

We previously reported that direct osmotic stimulation of the supraoptic nucleus (SON) of rats via a microdialysis probe produces a robust ‘rebound’ release of endogenous vasopressin (AVP) into the extracellular fluid of this hypothalamic nucleus (1). We now demonstrate in a combined microdialysis and push‐pull perfusion study that this intranuclear release is accompanied by increased AVP release in the septum. Simultaneous monitoring of intranuclear release and behavioral performance in the same animal indicated a significant correlation between the amount of endogenously released AVP and improved social memory based on the olfactory discriminative capacities of adult male rats. This memory improvement was partially blocked by local administration of a AVP V1 receptor antagonist either into the SON or septum. These findings indicate that direct osmotic stimulation of the supraoptic nucleus, which increases intracerebral vasopressin release, improves the acquisition and/or processing of olfactory stimuli. Thus, the endogenous neuropeptide fulfills one of the major criteria for being causally involved as a neurotransmitter/neuromodulator in behavioral performance.
Androgen Receptor Function During Undernutrition
Authors: Dong Qihan , Rintala Harri , Handelsman David J
Published: September 2006

Hypothalamo‐pituitary inhibition of reproductive function during undernutrition is well known, however, the physiological mechanisms leading to suppression of gonadotrophin secretion are not clear. A variety of studies have indicated that testicular negative feedback on LH secretion is enhanced during food restriction. To evaluate directly the suppression by endogenous androgens on hypothalamic GnRH pulse generator activity during food restriction and examine the mechanism underlying the increased testicular steroidal feedback, we examined (1) circulating bioactive LH (bLH) levels in response to selective cerebral androgen blockade by intraventricular administration of an androgen receptor antagonist (hydroxyflutamide, SCH 16423) and (2) the binding capacity and affinity of androgen receptors in medio‐basal hypothalamus, pituitary and prostate during undernutrition of intact mature male rats. Hydroxyflutamide (20 μg in 10μl vehicle), but not vehicle alone, markedly increased bLH levels in both food restricted and ad‐lib fed rats. However, the faster (geometric mean 11.4 vs 27.7 min) and greater (47.2 vs 21.9 ng/ml) increase in bLH level in food restricted compared with ad‐lib fed controls demonstrates an enhanced sensitivity to blockade of androgenic negative feedback during undernutrition. Food restriction increased androgen receptor binding capacity in pituitary (3.36 vs 0.77fmol/mg protein) but not in medio‐basal hypothalamus or prostate while binding affinity was unchanged by undernutrition in all 3 tissues. These studies reveal that undernutrition both enhances tonic, androgen receptor‐mediated feedback suppression of GnRH secretion and increases in pituitary (but not hypothalamic) androgen receptor numbers to cause inhibition of LH secretion.
Glutamate Inhibits Ingestive Behaviour
Authors: Bednar I. , Qian M. , Qureshi G. A. , Källström L , Johnson A. E. , Carrer H. , Södersten P.
Published: September 2006

Male rats treated with reserpine were motionless and ingested only a few of ten consecutive intraoral injections of a 1 M solution of sucrose. While injection of apomorphine, a dopamine agonist, stimulated locomotion and stereotyped sniffing in reserpinized rats, it did not reactivate ingestive responses. The non‐competitive N‐methyl‐D‐aspartate receptor antagonist MK801, however, stimulated locomotion as well as ingestion suggesting involvement of glutamate in the suppressive effect of resperpine on ingestive responses. A series of experiments was therefore undertaken to investigate the possible physiological role of glutamate in feeding.

For this purpose, we used Grill's intraoral intake test, in which the rat is infused intraorally with a sucrose solution and the amount ingested measured. In untreated rats, MK801 dose‐dependently facilitated ingestion of the sucrose solution and antagonized inhibition of ingestion by cholecystokinin octapeptide. Administration of cholecystokinin octapeptide or ingestion of sucrose increased the concentration of glutamate in the nucleus of the solitary tract, a brain stem relay transmitting sensory information from the gastrointestinal tract to the forebrain. MK801 was found to bind specifically to this brain area and block the elevation of glutamate and dopamine levels which occurred after treatment with cholecystokinin octapeptide in this neural site. Together these data suggest that dopamine and glutamate may interact within the nucleus of the solitary tract in controlling ingestive behaviour.
Testosterone Implants in Specific Neural Sites Activate Female Sexual Behaviour
Authors: Sharma Usha R. , Rissman Emilie F.
Published: September 2006

Sexual behaviour in most female mammals is regulated by oestrogen, often acting synergistically with progesterone. Moreover, the most important neural site of action for oestradiol is the ventromedial nucleus. In the female musk shrew, Suncus murinus, testosterone (T) activates sexual behaviour. Virgin females first engage in copulatory behaviour many hours in advance of follicular development and ovulation, when plasma oestradiol levels are very low. Testosterone, produced by the ovaries and the adrenal glands, must be aromatized centrally to oestradiol to initiate sexual behaviour. To identify the neural sites of action for T, ovariectomized females received unilateral hormone implants containing testosterone propionate. Hormone pellets were placed in 1 of several brain sites including the medial preoptic area and the dorsalmedial hypothalamus (DMH). Implants in either of these 2 sites, but not in the lateral preoptic area, internal capsule, nor anterior hypothalamus stimulated the induction of sexual behaviour. Hormone implants in the ventrolateral hypothalamus resulted in partially receptive animals. Immunocytochemistry was employed to determine which steroid receptors were present in the 2 behaviourally active sites. The medial preoptic area (MPO) and the dorsal and ventromedial hypothalamus both contain many cells that express oestrogen receptor immunoreactivity. A smaller subset of neurons in these regions are immunoreactive for androgen receptors. In summary, testosterone can act specifically in either the MPO or the DMH to induce female sexual behaviour. Both sites contain cells that express oestrogen and androgen receptors. Thus, testosterone may work via one or both of these steroid receptors to regulate behaviour. The results of these studies, and data collected previously, show that female sexual behaviour in this species is regulated by T and that this steroid can induce full sexual behaviour in 2 specific neural sites. Both of the sites of action identified in this experiment are critical for the expression of sexual behaviour in other species. The MPO has been shown to regulate male sexual behaviour via the aromatization of T to oestradiol in rodents and birds. The DMH is just dorsal to the ventromedial nucleus (VMN) which is essential for the regulation of sexual behaviour in female rodents. Further work is needed to determine if the neural circuitry for sexual behaviour in the musk shrew involves either the MPO or the VMN, if both areas are essential, or perhaps, the 2 regions regulate different aspects of female sexual behaviour.