ISSN:0953-8194    

DOI:10.1111/j.1365-2826.1992.tb00167.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

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 rep

ISSN:0953-8194    

DOI:10.1111/j.1365-2826.1992.tb00168.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractCorticotropin‐releasing factor (CRF) binding sites were found to be present in the rat vagus nerve and underwent axonal transport. Binding sites accumulated on both sides of ligatures placed on the nerve and at similar rates following ligation of right or left cervical vagal trunks of either male or female rats. CRF binding sites also accumulated proximal and distal to ligatures on subdiaphragmatic vagal trunks. Binding was specific, reversible and inhibited by the CRF receptor antagonist α‐helical‐CRF(9–41). [125l]Tyr0‐ovine‐CRF binding to rat vagus nerve was not guanine nucleotide‐sensitive. CRF and cholecystokinin binding sites were transported at a similar rate in the cervical vagus, although turnover of CRF binding sites was more rapid. No differences in CRF binding site transport were observed between Zucker rats of lean or

ISSN:0953-8194    

DOI:10.1111/j.1365-2826.1992.tb00169.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractThe distribution of putative melatonin receptors in the sheep has been investigated usingin vitroautoradiography and the high affinity, high specific activity ligand 2‐[125l]iodomelatonin. A wide distribution of specific labelling was found in both the ovine brain and pituitary gland as previously reported. Several novel areas of binding were also identified in the present study, including a fine layer of labelling at the medial edge of the diagonal band of Broca, the trigeminal nucleus, laminae II and III of the substantia gelatinosa, the molecular layer of the cerebellum as well as a scattered labelling in the pars distalis of the pituitary. There was no evidence of specific labelling in any of the peripheral tissues examined.Characterization studies performed on both neuronal and pituitary melatonin binding sites revealed that binding was time‐ and temperature‐dependent and reversible on addition of 1 μM melatonin. The binding of 2‐[125l]iodomelatonin was also competitively inhibited by increasing concentrations of 2‐iodomelatonin and melatonin. The inhibition constants (Ki) estimated for each of these substances were similar for both neuronal and pituitary sites. Saturation studies also revealed similarities between neuronal and pituitary tissues with 2‐[125l]iodomelatonin binding specifically to a single class of high affinity binding sites. Values for equilibrium constants (Kd) were within a range of 28 to 48 pM, and values were found to be not significantly different amongst the four regions of the brain investigated and the pars tuberalis of the pituitary. In contrast, the concentration of 2‐[125l]iodomelatonin binding sites (Bmax) ranged from 3 to 218fmol/mg protein and were maximal for the pars tuberalis.Saturation studies on brain and pituitary tissues taken from ewes killed either on the day of oestrus or during the luteal phase of the oestrous cycle, indicated that no differences exist in the affinity or concentration of 2‐[125l]iodomelatonin binding in any region between the two times of the cy

ISSN:0953-8194    

DOI:10.1111/j.1365-2826.1992.tb00170.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractOur recent observations in man suggested that the secretion of the thymic peptide, thymulin, is influenced by hormones of the pituitary‐adrenal axis. In the present study, we have used the rat as a model in order to examine 1) the effects of corticotrophin (ACTH) and glucocorticoids on the release of thymulin in vivo and in vitro, and 2) the influence of an acute rise in plasma thymulin on the secretion of corticosterone and luteinizing hormone.Immunoreactive thymulin was readily detectable in plasma from male Sprague‐Dawley rats(≃200 g). Chronic bilateral adrenalec‐tomy, which effectively removed endogenous corticosterone, produced highly significant (P0.2) from that in sham‐operated controls.In vitro, two non‐specific depolarizing agents, K+(56 mM) and veratridine (10 ≃M), caused significant (P<0.01) Ca2+‐dependent increases in thymulin release from segments of rat thymic tissue. Their effects were mimicked by ACTH1–39. The secretory responses to ACTH (0.025 to 1 ng/ml) were concentration‐dependent but a very high concentration (2 ng/ml) of the peptide was without effect. Dexamethasone (0.1 μM) reduced (P<0.05) the spontaneous release of thymulin in vitro but potentiated markedly (P<0.01) the secretory responses to ACTH (0.5 to 1.0 ng/ml).Administration of thymulin (0.1 and 10 μg/kg ip) produced, within 10 min, striking increases in the plasma thymulin concentration which were still evident at 30 min. The peptide concentration then declined rapidly and, within 24 h, was lower than that in the corresponding vehicle‐treated controls. The serum concentrations of corticosterone and luteinizing hormone were unaffected by the thymulin treatment. The saline vehicle (2.0 ml/kg ip) also produced a small increase in plasma thymulin concentration which was maximal at 10 min; a further small rise was evident 6 h after the injection but thereafter the thymulin values were indistinguishable from those in uninjected controls. A similar biphasic profile of serum corticosterone was apparent after the saline injection but the serum luteinizing hormone was unaffected.The results suggest that ACTH is a physiological enhancer of thymulin release and that, in certain circumstances, its effects may be potenti

ISSN:0953-8194    

DOI:10.1111/j.1365-2826.1992.tb00171.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

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

ISSN:0953-8194    

DOI:10.1111/j.1365-2826.1992.tb00172.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractGonadotropin secretion from the pituitary is regulated in large part by steroid action on the brain. An important question concerns whether luteinizing hormone‐releasing hormone (LHRH) neurons themselves transduce steroid signals, or whether, alternatively, steroid‐sensitive interneuronal populations regulate their activity. A previous study in the rat employing steroid autoradiography combined with LHRH immunocytochemistry revealed that only an exceedingly small percentage of LHRH‐immunoreactive (ir) neurons was estrogen concentrating. This study has examined the relationship of estrogen receptive and LHRH‐ir cells in the male and female guinea‐pig brain with double label immunocytochemistry. Since estrogen receptor‐ir, as demonstrated with antibody H222, is known to be confined predominantly to the cell nucleus, whereas LHRH‐ir is localized mainly in the cytoplasm, single cells can be double‐labeled. Diaminobenzidine tetrahydrochloride was used for localization of LHRH‐ir while nickel‐enhanced diaminobenzidine tetrahydrochloride was used for localization of estrogen receptor‐ir. The results revealed that there were many brain nuclei that contained both LHRH and estrogen receptor‐positive cells, including the preventricular periventricular nucleus, the anterior subcompact nucleus of the medial preoptic nucleus (MPNa), the remainder of the medial preoptic nucleus, the retrochiasmatic area, and the anterior, dorsomedial, ventrolateral and arcuate nuclei. However, of a total of 2,604 LHRH‐ir cells that were examined, we observed only 5 double‐labeled cells (<0.2%). The double‐labeled cells were not restricted to a single nucleus; they were present in the MPNa, the retrochiasmatic area and the arcuate nucleus. Moreover, at the light microscopic level, LHRH cells quite frequently appeared to be apposed to estrogen receptor‐positive cells (8.8% in the female), especially in the MPNa. These results lend further support to the notion that estrogen‐mediated regulation of the LHRH system is achieved primarily through estrogen receptive interneurons. However, due to the existence of LHRH‐LHRH synaptic interactions, the possibility also exists that a small population of estrogen‐sensitive LHRH neurons could contribute to gene

ISSN:0953-8194    

DOI:10.1111/j.1365-2826.1992.tb00173.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractActivation of hypothalamic α1‐adrenoceptors stimulates the secretion of corticotrophin‐releasing factors which in turn stimulate pituitary adrenocorticotrophin (ACTH). This mechanism is important in the physiological control of ACTH secretion. This study assesses the feasibility of using the ACTH response to release of endogenous catecholamines as a means of detecting a hypothalamic noradrenergic lesionin vivo. Intracerebroventricular infusion of the catecholamine neurotoxin, 6‐hydroxydopamine, was used to destroy noradrenergic nerve endings in rats, with the purpose of producing a model that could be used to study alterations in ACTH responses that may result from a lesion involving central noradrenergic neurons. 6‐Hydroxydopamine (250 μg icv) significantly reduced hypothalamic noradrenaline content, indicating damage to noradrenergic nerve endings, without affecting postsynaptic receptor function, as judged by preservation of the effect of a selective α1‐adrenergic agonist. Pharmacological release of endogenous catecholamines, effected by combined administration of a catecholamine precursor and an α2‐adrenergic antagonist, stimulated the secretion of ACTH in control, but not in 6‐hydroxydopamine‐treated rats. Degeneration of hypothalamic noradrenergic nerve endings is not followed by denervation hypersensitivity, and is therefore accompanied by impairment of the ACTH response to release of endoge

ISSN:0953-8194    

DOI:10.1111/j.1365-2826.1992.tb00174.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

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 fam

ISSN:0953-8194    

DOI:10.1111/j.1365-2826.1992.tb00175.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Abstractα1‐Adrenergic control of luteinizing hormone‐releasing hormone (LHRH) and galanin mRNA levels was examined in ovariectomized rats. Each rat was ovariectomized and a permanent bilateral cannula was implanted 1 mm dorsal to the preoptic area. Eleven to 14 days later, each rat received one of three treatments: prazosin (α1antagonist, n = 8), methoxamine (α1agonist, n = 5) or control (no drug, n = 7). Each drug was suspended in a polyacrylamide gel matrix and delivered to the preoptic area via the bilateral cannula. After 24 h of continuous exposure to the adrenergic agents (or control), rats were anesthetized, decapitated and brains were stored in liquid nitrogen until sectioned (7 μm) on a cryostat.In situhybridization was performed using a [32P]‐end‐labelled 59mer complementary to LHRH mRNA. Reduced silver grains, proportional to LHRH mRNA content, were quantified for number of LHRH cells per section, number of grains per labelled cell and total number of grains in labelled cells. Compared to the controls, prazosin caused a 32% decrease (P<0.05) in the number of cells expressing the LHRH gene. The LHRH cells from untreated animals had a median of 53 grains/cell with a smooth distribution above and below the median. Treatment with prazosin reduced the median number of grains/cell to 36 (P<0.05). When the number of grains in labelled cells were totalled, prazosin decreased (P<0.01) the number of grains by 47%. Surprisingly, methoxamine caused no quantitative changes in any of the parameters examined. This might be explained if LHRH transcription in control animals was proceeding at near‐maximal rates supported, in part, by an endogenous α1ligand. Alternatively, continuous exposure to this agonist may have resulted in desensitization to its stimulatory effects. When anatomically matched brain tissue sections from these animals were examined for galanin mRNA, no differences among experimental groups were detected. In conclusion, administration of an α1‐adrenergic antagonist into the preoptic area suppressed levels of LHRH mRNA but not galanin mRNA. Therefore, the data suggest that an endogenous α1ligand, such as norepinephrine (or epinephrine), is required to maintain a high level of LHRH gene expression in the

ISSN:0953-8194    

DOI:10.1111/j.1365-2826.1992.tb00176.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY