bluuebunny/crossref_metadata_2025_split huggingface dataset:
Progesterone Receptor‐Containing Neurons in the Guinea‐Pig Mediobasal Hypothalamus have Axonal Projections to the Medial Preoptic Area
Authors: Warembourg Maryvonne , Poulain Pierre , Jolivet André 
Published: September 2006

AbstractThe location and number of progesterone receptor‐containing neurons in the mediobasal hypothalamus that project to the medial preoptic area were determined by combining retrograde fluorescent tract tracing with progesterone receptor immunocytochemistry. Injections of the retrograde tract tracer Fluoro‐gold were made in the preoptic area of female guinea‐pigs ovariectomized and primed with estradiol. After 5 days survival to allow for retrograde transport, tissue sections were incubated with monoclonal antibodies to the progesterone receptor to detect the presence of progesterone receptor‐immunoreactive neurons.Cell bodies were labelled with Fluoro‐gold throughout the arcuate nucleus. These neurons were not concentrated in any particular area of the nucleus but were diffusely distributed bilaterally. Retrogradely‐labelled neurons were also observed in the ventrolateral and ventromedial nuclei mainly contralateral to the injection site. Progesterone receptor immunofluorescence labelled a subpopulation (7% to 10%) of these retrogradely‐labelled cells particularly in the arcuate nucleus, including the median eminence. The double‐labelled cells were more numerous in the anterior two‐thirds of the arcuate nucleus. Although our estimates of the proportion of hypothalamic progesterone receptor‐immunoreactive neurons that sent axons directly to the medial preoptic area were low, (about 0.35%), these neurons may be part of a neural circuit involved in the regulation of reproductive processes.
Development of Oxytocinergic Neurons in Monolayer Cultures Derived from Embryonic, Fetal and Postnatal Rat Hypothalami
Authors: Madarász E. , Környei Z. , Poulain D. A. , Theodosis D T. 
Published: September 2006

AbstractMonolayer cultures from hypothalami of embryonic, fetal and postnatal rats were established to study the development of oxytocin‐secreting neurons in vitro. Particular culture conditions, known to enhance the survival and growth of different types of neural cells in vitro, were used to investigate the conditions necessary for the appearance and survival of these peptide‐producing cells in culture. They included increasing the concentration of potassium in the culture milieu and/or the addition of triiodothyronine (T3). The use of immunocytochemical procedures with a monoclonal antibody that recognizes oxytocin‐associated neurophysin (NP‐OT) and polyclonal antibodies specific for oxytocin permitted us to identify the neurons. In cultures derived from embryonic (E16‐E17) hypothalami, no NP‐OT‐ or oxytocin‐positive neurons were detected and their appearance could not be provoked by increasing extracellular potassium concentration or by administration of T3. On the other hand, in cultures obtained from fetal (E18‐E19) rat hypothalami, a few neurons showed immunoreactivity for NP‐OT (but not for oxytocin); the immunoreactivity was localized essentially in somata and proximal portions of neurites. When 108 M T3 was included in the culture medium, there were cells showing immunoreactivity not only for NP—OT, but also for oxytocin, visible in somata and in dendritic‐ and axonal‐like processes. In comparison, T3 did not influence the total number of neurons developing in these cultures. Lastly, in cultures derived from young postnatal (PO—P2) rat hypothalami, NP—OT‐ and oxytocin‐immunopositive neurons were found regularly; their appearance did not require any special pretreatment of the cultures. In all cultures, high extracellular potassium concentration (25 mM) resulted in a general improvement in the survival of neurons but did not induce the appearance of more oxytocin‐immunoreactive cells. Our observations support in vivo results showing that although presumptive oxytocin‐producing cells appear early in the development of the hypothalamus, their maturation, and in particular, their ability to produce oxytocin, occurs late at the time of birth. A factor that selectively enhances their differentiation, is the thyroid hormone, T3.
Spontaneous Intracellular Calcium Oscillations and Gsα Subunit Expression are Inversely Correlated with Secretory Granule Content in Pituitary Cells
Authors: Chiavaroli Carlo , Cooper Dermot M. F. , Boyajian Christine L. , Murray‐Whelan Rosemary , Demaurex Nicolas , Spiegel Allen M. , Schlegel Werner 
Published: September 2006

AbstractCells of the pituitary tumour cell line GH4C1 were exposed to epidermal growth factor, estradiol and insulin for 5 days, a treatment which resulted in 1) increased prolactin storage in secretory granules, 2) the loss of spontaneous [Ca2+]1 oscillations, and 3) a selective reduction of the protein Gsα, seen in immunoblots, cholera toxin labelling, and vasoactive intestinal peptide stimulation of adenylyl cyclase. In contrast, the glucocorticoid dexamethasone, which increases the expression of Gsα, partially restored spontaneous [Ca2+]1 oscillations and decreased prolactin storage. It is concluded that Gsα levels in tumoral cells result in spontaneous electrical activity which may empty prolactin stores by the continuous activation of exocytosis.
Melatonin Regulates the Synthesis and Secretion of Several Proteins by Pars Tuberalis Cells of the Ovine Pituitary
Authors: Morgan Peter J. , Barrett Perry , Davidson Gary , Lawson Wilfred 
Published: September 2006

AbstractThe pars tuberalis (PT) of the pituitary may be an important target for melatonin action, but the secretory output of the melatonin‐responsive cells is unknown. Using [35S]methionine, protein synthesis and secretion have been studied in primary cultures of ovine PT cells, and analysed by sodium dodecyl sulphate‐polyacrylamide gel electrophoresis. Only 4% of the labelled proteins appeared in the medium with the majority retained in the cells. Stimulation of the cells with 10μM forskolin increased the accumulation of several labelled proteins in the medium without corresponding changes in the cell (72, 62, 44, 39, 29, 24, 23, 18 and 14 kd). Two‐dimensional gel electrophoresis showed the proteins to have mildly acidic isoelectric points. Melatonin (1 μM) counteracted the stimulatory effect of forskolin on all but one (23 kd) of these secreted proteins. Immunoprecipitation showed this to be prolactin. Furthermore, melatonin alone appeared to have an inhibitory effect on the synthesis and release of proteins into the medium. The synthesis and secretion of the melatonin‐responsive proteins was not inhibited by actinomycin D (1 μg/ml), indicating control at the translational level. This contrasts with the regulation of prolactin which is actinomycin D‐sensitive. Pulse‐chase experiments demonstrated that it requires 30 min for the secretory proteins to appear in the medium, consistent with intracellular processing and packaging prior to secretion. The secretory proteins labelled in the ovine PT, and responsive to melatonin, did not appear to be specific to the PT, as a similar profile of labelled secretory proteins was produced in primary cultures of pars distalis cells. However, melatonin had no effect on the synthesis and secretion of proteins by the pars distalis. These results demonstrate that in the ovine PT melatonin regulates the synthesis and export of several secretory proteins. These are possibly packaging proteins of secretory granules, similar to the granin family of proteins. Thus, the results confirm that melatonin‐responsive cells are secretory cells and further imply that the PT‐specific product is not a protein.
Glucocorticoids are Required for Food Deprivation‐Induced Increases in Hypothalamic Neuropeptide Y Expression
Authors: Ponsalle Patricia , Srivastava Laxmi S. , Uht Rosalie M. , White Jeffrey D. 
Published: September 2006

AbstractNeuropeptide Y (NPY), a 36 amino‐acid peptide found within the hypothalamus, is thought to be an important regulator of food intake. Hypothalamic NPY gene expression, synthesis and secretion are all known to be increased in models of increased metabolic demand in which serum glucocorticoids are also elevated. The present studies were designed to test the hypothesis that glucocorticoids are required for increased hypothalamic preproNPY mRNA levels induced by food deprivation (FD). First, animals underwent bilateral sham‐adrenalectomy (sham) or not (control), and were subjected to 72 h FD, or not. Total RNA was isolated from hypothalamic tissue blocks and the content of preproNPY mRNA was measured by solution hybridization/RNase protection analysis. This study revealed that there was no significant difference in hypothalamic preproNPY mRNA content between shamfed and control‐fed groups, or between sham‐FD and control‐FD groups. In the second experiment, animals underwent bilateral adrenalectomy (ADX), were allowed to feed ad libitum and were sacrificed 1 day, 4 days and 7 days after ADX. Nuclease protection analysis revealed no significant effect of ADX on hypothalamic preproNPY mRNA levels over this time‐course. Finally, we examined the role of glucocorticoids in regulating NPY gene expression following FD. Animals underwent bilateral ADX, or not. At the time of surgery, ADX animals received placebo, or corticosterone (B) replacement in the form of constant release pellets, at one of two doses. Food was removed from half of the animals in each group 24 h after surgery; all animals were sacrificed 72 h thereafter. There was no difference in preproNPY mRNA content between the ADX‐FD and ADX‐fed groups, relative to the fed controls. Replacement with corticosterone [ADX(B)] did not alter preproNPY mRNA content in fed animals, however preproNPY mRNA content in FD animals was increased 2.5‐fold. These studies demonstrate that glucocorticoids are necessary and serve a stimulatory role in the increase in hypothalamic preproNPY mRNA levels observed under conditions of FD, and suggest that hypothalamic NPY gene expression may be directly responsive to peripheral metabolic and hormonal signals.
Oestrogen Positive Feedback Reduces Arcuate Proopiomelanocortin Messenger Ribonucleic Acid
Authors: Rosie R. , Thomson E. , Blum M. , Roberts J. L. , Fink G. 
Published: September 2006

AbstractOestradiol‐17ß, in its positive feedback mode, as well as stimulating the release of luteinizing hormone‐releasing hormone. (LHRH), also stimulates LHRH mRNA synthesis in medial preoptic neurons. Our aim was to determine whether the action of oestradiol might be mediated in part by inhibiting arcuate proopiomelanocortin (POMC) neurons which terminate on LHRH neurons. Female rats were ovariectomized at about 1000 h of dioestrus, given a subcutaneous injection of oil or oestradiol benzoate and killed at 1600 h the same day (presumptive dioestrus), presumptive pro‐oestrus and oestrus and at 1000 h of presumptive pro‐oestrus. In situ hybridization of brain sections was carried out with a [35S]UTP‐labelled riboprobe containing 538 bases of a cDNA identical to exon 3 of the POMC gene, which includes the ß‐endorphin coding domain. The amount of POMC mRNA in cells of the anterior arcuate nucleus, as assessed by grain counts, was significantly decreased in oestradiol benzoate‐ compared with oil‐treated animals at 1600 h of pro‐oestrus, but at none of the other times studied. This finding, together with other data, suggests that the positive feedback stimulation of LHRH mRNA synthesis by oestradiol‐17ß may be due, in part, to the disinhibition of LHRH neurons consequent on inhibition of POMC mRNA biosynthesis in arcuate neurons.
The Role of the Mu1 Opioid Receptor Subtype in the Regulation of Prolactin and Growth Hormone Secretion by Beta‐Endorphin in Female Rats: Studies with Naloxonazine
Authors: Janik James , Callahan Phyllis , Rabii Jamshid 
Published: September 2006

AbstractThe μ opioid receptor subtype has been reported to mediate the prolactin secretory response to opioids. This receptor subtype has been implicated in the morphine‐induced prolactin increase, as well as the prolactin response to μ‐specific opioid peptides. Subtypes of the μ receptor have been proposed and the μ1, site has been postulated as the receptor subtype involved in the morphine‐induced prolactin secretory response. However, the role of this receptor subtype in mediating the endocrine effects of the endogenous opioid peptides has not been characterized. In order to determine the physiological significance of this receptor subtype, animals were pretreated with saline, WIN 44,441–3 (a μ, δ and κ antagonist) or naloxonazine (a μ1 antagonist) followed by a stimulatory dose of morphine or β‐endorphin. A dose response study for β‐endorphin was conducted to determine the minimal stimulatory dose of β‐endorphin on the prolactin and growth hormone (GH) secretory response. The dose response study indicated that β‐endorphin is a more potent stimulus for prolactin release than for GH. A dose as low as 25 ng increased prolactin levels as much as 100‐fold in both lactating and diestrous female rats. In contrast, 2.5 μg β‐endorphin was required in order to consistently and significantly increase circulating levels of GH by 2‐ to 3‐fold. WIN 44,441–3 antagonized the stimulatory effects of β‐endorphin on both prolactin and GH secretion. Naloxonazine pretreatment abolished the morphine‐induced prolactin secretory response, without affecting the GH increase in diestrous females. Naloxonazine also antagonized the prolactin response to β‐endorphin in both lactating and diestrous females. In addition, it attenuated the GH secretory response but did not totally abolish it. These data indicate that β‐endorphin elicits an increase in prolactin release through an opioid specific receptor which appears to be the μ1 opioid receptor subtype. They further suggest that β‐endorphin may increase GH levels, at least partially, via its action at this μ1 site.
Novel Hypothalamic and Preoptic Sites of Prepro‐Melanin‐Concentrating Hormone Messenger Ribonucleic Acid and Peptide Expression in Lactating Rats
Authors: Knollema S. , Brown E. R. , Vale W. , Sawchenko P. E. 
Published: September 2006

AbstractThe deduced structure of the rat melanin‐concentrating hormone (MCH) precursor predicted the existence of at least two peptides that may be processed from it, one similar to teleost MCH and a second novel neuropeptide, NEI. Cellular localization studies confirmed that prepro‐MCH (ppMCH) mRNA and the MCH and NEI peptides are expressed predominantly in cells in the zona incerta and caudal lateral hypothalamic area with minor contingents seen in the olfactory tubercle and pons. A moderate MCH‐and NEI‐immunoreactive axonal projection to the median eminence and, particularly, to oxytocin‐rich regions of the posterior pituitary suggested some anatomical heterogeneity of ppMCH‐expressing neurons in the hypothalamus, and an involvement in neuroendocrine function. In the present study, immunohistochemical and hybridization histochemical methods were used to follow MCH gene and peptide expression as a function of reproductive status in female rats. Nursing dams sacrificed after 8 to 21 days of lactation consistently displayed ppMCH mRNA and MCH and NEI immunoreactivity in a discrete and contiguous band, encompassing the ventral aspect of the medial part of the medial preoptic nucleus, the periventricular preoptic nucleus, and the most rostral aspects of the paraventricular nucleus of the hypothalamus (PVH). Combined immunohistochemical (for oxytocin) and hybridization histochemical (for ppMCH mRNA) staining failed to reveal a significant degree of congruence in the two chemically‐specified cell populations in the PVH of lactating dams. The apparent induction of ppMCH‐derived peptides and mRNA in the preoptic area and PVH was not apparent in animals sacrificed 4 to 8 days after weaning, during late pregnancy, or at any point in the estrous cycle. Moreover, no frank alterations in ppMCH mRNA were evident in the principal sites at which ppMCH is expressed at constitutively high levels, i.e. in the lateral hypothalamic area and zona incerta, as a function of reproductive status. The loci and apparent state‐dependency of the induction of ppMCH mRNA and peptide expression suggests a role for these gene products in the control of lactation.
Evidence that Release of Dopamine in the Brain is Involved in the Inhibitory Effect of Cholecystokinin Octapeptide on Ingestion of Intraorally Administered Sucrose in Male Rats
Authors: Bednar I. , Qureshi G. A. , Södersten P. 
Published: September 2006

AbstractTo study the possibility that release of dopamine in the brain mediates the inhibitory effect of Cholecystokinin octapeptide on ingestive behaviour, the effect of amphetamine on intake of pellets or an intraorally administered sucrose solution was compared with that of Cholecystokinin octapeptide. Additionally, comparisons were made between the effect of Cholecystokinin octapeptide and pargyline, a monoamine oxidase inhibitor, and α‐methyl‐ρ‐tyrosine, a tyrosine hydroxylase inhibitor. While amphetamine dose‐dependently inhibited pellet intake it failed to inhibit sucrose intake in doses which caused behavioural stereotypies (<800 μg). Cholecystokinin octapeptide (5 μg) inhibited ingestive behaviour in both tests. A very high dose of amphetamine (2 mg) was required to inhibit sucrose intake to a level comparable to that of Cholecystokinin octapeptide. Pargyline (5 to 25 mg) or α‐methyl‐p‐tyrosine (25 to 100 mg) dose‐dependently inhibited pellet intake but had only weak effects on the intake of sucrose. Pargyline increased the concentration of dopamine and 3‐methoxytyramine in the dorsal striatum and decreased the concentration of 3,4‐dihydroxyphenylacetic acid. α‐Methyl‐ρ‐tyrosine decreased the concentration of dopamine and 3,4‐dihydroxyphenylacetic acid, but not that of 3‐methoxytyramine. Injection of amphetamine (2 mg), but not Cholecystokinin octapeptide, in rats pretreated with pargyline increased the concentration of 3‐methoxytyramine in the dorsal striatum and this effect was blocked by pretreatment with α‐methyl‐ρ‐tyrosine. Pretreatment with α‐methyl‐ρ‐tyrosine partially reversed the inhibitory effect of Cholecystokinin octapeptide on sucrose ingestion, enhanced the effect of amphetamine but did not affect that of apomorphine, a dopamine agonist. The results support the possibility that the inhibitory effect of Cholecystokinin octapeptide on consummatory ingestive behaviour, in part, is mediated via release of dopamine in the brain.
Stress Affects the Activated Form of the Corticosteroid‐Receptor Complex in the Rat Brain
Authors: Maroulakou Ioanna G. , Kitraki Efthimia , Stylianopoulou Fotini 
Published: September 2006

AbstractGlucocorticoid actions in the brain, particularly in the hippocampus and the hypothalamus, are critically involved in the response of the organism to stress. The key molecules in this process are the corticosteroid receptors, which upon activation, migrate and act in the nucleus. We have investigated the effect of stress on the activated form of the cytosolic glucocorticoid receptor from the above brain areas, using anion exchange chromatography. Exposure of rats to chronic stress resulted in the disappearance of the chromatographic peak, which corresponds to the activated form (DE II) of the hormone‐receptor complex. For this phenomenon to occur, 1) the animal must be exposed to chronic, and not to acute stress, and 2) the adrenals of the animal must be intact. The disappearance of the activated form of the hormone‐receptor complex (DE II) following chronic stress is most probably due to proteolysis of the receptor molecule, since it is specifically inhibited by the protease inhibitor leupeptin. This phenomenon may represent an adaptive mechanism which helps the organism cope with a repeated stressor.
Immunocytochemical Localization of 11 Beta‐Hydroxysteroid Dehydrogenase in Hippocampus and Other Brain Regions of the Rat
Authors: Sakai Randall R. , Lakshmi Vijaya , Monder Carl , McEwen Bruce S. 
Published: September 2006

AbstractThe dehydrogenase form of 11 β‐hydroxysteroid dehydrogenase (11‐DH) which catalyzes the oxidation of the biologically active steroid, corticosterone, to its inactive metabolite, 11‐dehydrocorticosterone, is found in rat brain. The distribution and localization of 11‐DH‐like labeling in the rat brain was examined by immunocytochemistry. 11‐DH‐like immunostaining was found in all subfields of the hippocampus and in many other parts of the brain, including the preoptic area (POA), central nucleus of the amygdala, bed nucleus of the stria terminalis (NIST) and the cerebral cortex. Percentages of 11‐DH‐positive cells ranged from 10% in the POA and NIST to 50% to 60% in the hippocampus. When combined with neuronal or glial markers, 11‐DH‐like immunostaining was found to be predominantly localized within neurons, ranging from 10% or less glial labeling in hippocampus, amgydala and cortex to 22% glial labeling in the POA and NIST. Immunostaining was present in both the cytoplasmic and nuclear components of some cells in addition to their projections. In the kidney, 11‐DH has been postulated to be a key component in a mechanism by which aldosterone gains access to renal Type I receptors despite the presence of much higher concentrations of glucocorticoids. The present data is consistent with a similar mechanism occurring in at least some parts of the brain, although the hippocampus appears to be an important exception because it does not appear to be differentially responsive to aldosterone in spite of its high 11‐DH activity and immunoreactivity. However, the hippocampus is not implicated in neural control of salt appetite and fluid balance, whereas some of the other brain regions like the POA, NIST and amygdala are believed to be involved. Other aspects of 11‐DH localization must therefore be examined in future studies, including the co‐presence of mineraiocorticoid receptors and 11‐DH in the same or adjacent cells and the possible significance of the relatively high glial localization of 11‐DH immunoreactivity in the POA and NIST.