摘要:

The factors regulating oxytocin expression have not yet been characterized in detail. Although direct control by ligand‐dependent binding of nuclear hormone receptors to the oxytocin promoter has been suggested, the presence of these receptors in the tissues expressing oxytocin has not been shown consistently. We have analyzed nuclear proteins from preovulatory bovine granulosa cells and corpus luteum, tissues actively expressing the oxytocin gene, and describe here the characterization of a tissuespecific factor binding to the conserved element in the oxytocin promoter that has been implicated in the control of this gene. This factor is the bovine homologue of SF‐1, an orphan receptor expressed specifically in steroidogenic tissues. It is suggested that SF‐1 binds to the oxytocin promoterin vivoand is involved in control of oxytocin gene expression possibly by interaction with other fa

ISSN:0953-8194    

DOI:10.1111/j.1365-2826.1994.tb00546.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractThe mechanisms by which oestrogen modulates the biosynthetic and secretory activity of magnocellular oxytocin neurones are poorly understood. Using an antibody directed against the oestrogen receptor (ER), the distribution of ER‐immunoreactive (‐IR) cells in relation to the supraoptic nucleus (SON) was examined. Although no ER‐IR cells were detected within the SON, a small population of immunoreactive cells separate from those in the preoptic area was identified in the perinuclear zone of the SON. Double‐labelling experiments with an antibody specific for glutamic acid decarboxylase (GAD), the neuronal enzyme producing gamma aminobutyric acid (GABA), revealed that approximately 60% of perinuclear zone ER‐IR cells contained GAD. A further set of immunocytochemistry experiments using an antibody raised against the β2. and β3sub‐units of the GABAAreceptor revealed immunoreactivity in the SON. Double‐labelling experiments demonstrated that both oxytocin‐IR and non‐oxytocin‐IR neurones in the SON were immunoreactive for β2and/or β3sub‐units of the GABAAreceptor. These studies have identified ERs within a GABAergic neural population in the perinuclear zone of the SON and shown that magnocellular oxytocin neurones in the SON possess GABAAreceptors comprised of β2and/or β3sub‐units. In conjunction with previous evidence that the perinuclear zone GABA neurones are an important source of GABA terminals in the SON, these results provide a morphological basis for the hypothesis that perinuclear zone GABA neurones may be part of a steroid‐sensitive neural circuitry transmitting oestrogen input

ISSN:0953-8194    

DOI:10.1111/j.1365-2826.1994.tb00547.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

ISSN:0953-8194    

DOI:10.1111/j.1365-2826.1994.tb00548.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractInduction of the c‐fosprotein product (Fos) was used to immunocytochemically identify oxytocin (OT) neurons that may be activated during copulatory interactions. Fos induction was quantified in sexually‐experienced male rats after either (a) exposure to a testing arena recently vacated by an estrous female, (b) copulatory interactions such as mounting and intromission without ejaculation, or (c) mounting and intromissions culminating in ejaculation. In the parvocellular regions of the paraventricular nucleus of the hypothalamus (PVN), the number of neurons expressing Fos increased following either intromission (53%) or ejaculation (124%). Significant, but less striking, increases in the number of cells expressing Fos were noted in magnocellular regions of the PVN where intromission resulted in a 13% increase and ejaculation in a 49% increase in Fos. The number of perikarya immunoreactive for OT and AVP did not differ as a function of increasing sexual contacts. In control (novel arena) males, 33–73% of the Fos labeling occurred in OT cells. Sexual interactions did not enhance the number of double‐labeled cells in most parvocellular regions. However, in lateral parvocellular regions located in the most caudal aspects of the PVN, 31% of the Fos‐positive cells occurred in OT neurons in ejaculated males, while in control males none of the OT cells were double‐labeled. This PVN subdivision is known to consist of neurons that project to the brain stem and spinal cord at lumbar levels which contain motor neurons that regulate penile reflexes. The present data suggest a possible neurochemical circuit which incorporates oxytocinergic neurons in the mediation of masculine sexua

ISSN:0953-8194    

DOI:10.1111/j.1365-2826.1994.tb00549.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractAcute 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‐translatio

ISSN:0953-8194    

DOI:10.1111/j.1365-2826.1994.tb00550.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractThe 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 isnotessential 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 ACTH1–39concentrations 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 PGE2concentrations 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 parturiti

ISSN:0953-8194    

DOI:10.1111/j.1365-2826.1994.tb00551.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractWe have previously demonstrated that TRH induces several hypophyseal cell type differentiation. In the present study, we re‐evaluated the effect of GnRH on gonadotroph differentiation, and we determined whether gonadotropin is implicated in the appearance of other pituitary cell types. These effects were compared to the influence of TRH on LH and TSH cell differentiation. Pituitary primordia of 11 day‐old rat embryos were cultured in a synthetic medium until the equivalent of term, and the LH and TSH cell differentiation was visualized using an immunohistochemical technique. The effect of GnRH on pituitary hormone cells was evaluated by measuring the percentage of immunoreactive area per section.GnRH, when added on the first day of culture, induced LH and TSH cell differentiation in a dose‐dependent manner. GnRH was more effective than TRH in inducting gonadotropic phenotype expression. This suggests that GnRH, which evokes LH release, is the most effective factor inducing gonadotroph differentiation in early fetal life. However, GnRH was as effective as TRH in thyrotroph differentiation. Lactotrophs were detected in primordia cultured with GnRH. As lactotroph phenotype differentiation is controlled by the a‐subunit of glycoproteic hormone, further studies are required to determine whether or not GnRH effect on lactotroph is direct. GnRH did not affect the corticotroph and somatotroph differentiation. These results confirm that hypothalamic factors such as TRH or GnRH are capable of inducing more than one pituitary cell phe

ISSN:0953-8194    

DOI:10.1111/j.1365-2826.1994.tb00552.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractThe molecular mechanisms regulating GABAAreceptor activity in cultured frog melanotrophs were studied using the patch‐clamp technique. In the whole‐cell configuration, application of GABA evoked a dose‐related increase of inward chloride currents. The ED50value, estimated from the sigmoidal dose‐response curve was 2 × 10−6M and the Hill coefficient was 1.55. The amplitude of the GABA‐induced current decayed with time. Kinetics analysis of the desensitization revealed that the time‐course of the current decrement was fitted by one exponential. Graded doses of GABA or association of GABA with the benzodiazepine receptor agonist flunitrazepam accelerated the desensitization process. In contrast, the time‐course of the current did not significantly vary at different holding potentials. In the outside‐out configuration, GABA was found to activate channels which displayed three unitary conductance levels (8, 15 and 30 pS). The channel openings of the more frequent conductance level (30 pS) exhibited short and long lasting open states (1.2 and 28.3ms at ‐60mV). Altogether these data reveal that frog melanotrophs possess a single population of GABAAreceptors which interconvert into a higher affinity state in the presence of benzodiazepine receptor agonists. Two GABA molecules must bind to the receptor to trigger long lasting channel openings. In addition, the activity of the GABAAreceptor appears to be independent of the accumulation of intrace

ISSN:0953-8194    

DOI:10.1111/j.1365-2826.1994.tb00553.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractPrevious studies have suggested an involvement of enkephalins in regulation of oxytocin (OXT) and vasopressin (AVP) release, which seems to disagree with the very low affinities of Met‐ and Leu‐enkephalin for the kappa opioid receptor. As opioid receptors in the neural lobe exclusively exist of kappa receptors, we studied the binding characteristics of larger pro‐enkephalin derived peptides for opioid binding sites in the neural lobe by means of light microscopic receptor autoradiography. In addition, the pharmacological characteristics of opioid binding sites in the neural lobe were compared with those in other parts of the pituitary.In the neural as well as the intermediate lobe both high and low affinity3H‐bremazocine binding sites were present. Binding to these sites was completely displaceable by both naloxone and nor‐binaltorphimine, suggesting that these sites represent kappa opioid receptors. Also with regard to selectivity and affinity characteristics to other ligands, opioid binding sites in the neural and intermediate lobe were quite similar. In the anterior lobe a very low level of bremazocine binding was present, which could not be displaced by nor‐binaltorphimine.Displacement studies with pro‐enkephalin and pro‐dynorphin derived peptides showed that both groups of peptides could bind to opioid binding sites in the neural and intermediate lobe. Especially the relatively large pro‐dynorphin and pro‐enkephalin derived peptides, such as dynorphin 1–17 and BAM22, appeared to be very potent ligands for these opioid binding sites and were much more potent than smaller fragments, such as dynorphin 1–8, and Met‐ and Leu‐enkephalin. These results contradict the existence of a mismatch in the neural (and intermediate) lobe with regard to the local type of opioid pep

ISSN:0953-8194    

DOI:10.1111/j.1365-2826.1994.tb00554.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractOur previous reports of major sex differences in the substance P‐immunoreactive (SPir) innervation of the medial posterior divisions of the bed nucleus of the stria terminalis (BST) and medial nucleus of the amygdala in rats raised the question of the hormonal regulation of this innervation. We now report the results of two experiments which examined the effects of castration of adult males on the SPir innervation of these regions. In experiment 2 we asked whether castration might also alter the cytoarchitecture of these regions.In experiment 1 three groups; sham operated (Sham), castrated (C) and castrated plus testosterone (C + T) were examined at each of the three survival periods (2, 4 and 8 weeks) post castration. Animals of the C + T groups each received a 45 mm silastic implant of testosterone sc at the time of castration to maintain testosterone levels postoperatively. Castration produced a consistent and highly significant decrease in the area of dense SPir fiber staining in the posterior medial amygdala which became greater with increasing survival. By 8 weeks the area of staining was 42% smaller in group C as compared to the matched sham‐operated group. Smaller decreases were seen in the size of the dense field of SPir fibers in the posterior part of the dorsomedial BST. Testosterone implants maintained the size of the SPir fields of fibers in both the medial amygdala and BST, as the areas of staining in the C + T groups were not significantly different from those in the Sham groups at any of the 3 survival times.In experiment 2 we measured the area and optical density of SPir fiber staining in the medial amygdala and medial BST at 8 weeks post‐castration. In addition, we measured the size of the cell groups within these regions using cresyl‐stained sections. As in experiment 1, at 8 wks following castration there was a marked decrease in the area of dense SPir staining in both the BST and medial amygdala. The sizes of the dense fields of fibers were reduced by approximately 23% in the BST and by 40% in the posterior medial amygdala. Castration also significantly reduced the optical density of staining within the medial amygdala. The major finding of experiment 2 is that castration affects the cytoarchitecture as well as the SPir staining in these areas. In the BST, the cell group BSTMPM receives most of the dense SPir innervation. Gonadectomy reduced the size of BSTMPM by approximately 28%. In the amygdala, the cell group MePD receives most of the dense SPir innervation. Gonadectomy reduced the size of MePD by approximately 27%, while its neighbour MePV was reduced by a similar degree (26%). These atrophic changes are at least somewhat specific, as other features such as brain weight, the overall size of the forebrain as estimated from whole coronal sections, and the size of the suprachiasmatic nucleus were unchanged. The atrophic changes in the cytoarchitecture of the posterior medial amygdala and BST suggest that the changes in SPir staining seen in experiments 1 and 2 may be secondary to structural atrophy, including reduced axonal and dendritic branching, of hormone responsive SP‐containing neurons. The time course of the response to castration demonstrated in experiment 1 suggests that these changes in SP‐containing neurons are relevant to the gradual decline in male sexual behavior which follows

ISSN:0953-8194    

DOI:10.1111/j.1365-2826.1994.tb00555.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY