摘要:

In situ hybridization histochemistry was used to locate cells containing tyrosine hydroxylase (TH) mRNA in the hypothalami of salt-loaded and Brattleboro rats. The hyperosmotic plasma conditions found in these animals, as compared to control animals, was associated with an increase in detectable TH mRNA-producing cells in the paraventricular and supraoptic nuclei. These results suggest that dopamine synthesized by neurons of those nuclei may participate in the regulation of neuropeptide synthesis and release within the nuclei and the posterior pituitary.

ISSN:0028-3835    

DOI:10.1159/000124858

出版商:S. Karger AG    

年代:1987

数据来源: Karger

摘要:

Immature and adult female rats were bilaterally implanted in the medial preoptic area (MPOA) or hypothalamic ventromedial-arcuate region (VMAR) with the dopamine (DA) antagonist, pimozide, or the DA agonist, apomor-phine, and the sensitivity to the LH-inhibiting effect of a subcutaneous injection of estradiol benzoate (EB), the onset of puberty and ovarian cyclicity were investigated. Diminution of the inhibitory effect of EB on LH secretion was recorded in ovariectomized immature and adult females implanted in the MPOA with pimozide. This response was not obtained in rats implanted in the VMAR. In contrast, medial preoptic, but not intrahypothalamic, implantation of agar pellets containing apomorphine resulted in enhanced sensitivity to estrogen both prepubertally and during the ovarian cycle. The sensitizing effect of apomorphine was completely prevented in prepubertal rats by pretreatment with EB for 6 days. Bilateral implantation of pimozide-agar pellets in the MPOA of 28-day-old intact females induced significant advancement of the onset of puberty, whereas sexual maturation was not affected by daily subcutaneous injections of the DA antagonist from day 28 till the day of vaginal opening. In adult 4-day-cyclic rats fitted with guide cannulae, the forthcoming ovulation was delayed for about 7 days as compared to the controls implanted with agar if apomorphine was placed in the MPOA from the morning of metestrus to the morning of diestrus. Similar implants located in the VMAR were ineffective in this regard. The results suggest that: (1) low DA activity in the MPOA reduces and high activity enhances the sensitivity of the negative estrogen feedback in immature and adult female rats; (2) the medial preoptic DA activity seems to be involved in the control of female puberty and of the ovarian cycle, and (3) a relationship may exist between the estrogen-induced prepubertal and preovulatory desensitization of the negative estrogen feedback and the DA neurotransmission in the MPOA.

ISSN:0028-3835    

DOI:10.1159/000124859

出版商:S. Karger AG    

年代:1987

数据来源: Karger

摘要:

Using specific antibodies to corticotrophin-releasing factor (CRF) and arginine vasopressin (AVP) we have immunocytochemically located cells and fibres containing these peptides in sheep fetuses. CRF neurones were first detected, in low frequency, in the paraventricular nuclei of fetuses of 90 days of gestation (term is 142–152 days), although no connections to the median eminence (ME) were apparent until 105 days of gestation. AVP neurones were found from 42 days of gestation, the earliest stage examined, and at this age, fibres and terminals were present mainly in the external lamina of the ME. At subsequent ages there appeared to be a redistribution of AVP fibres such that by 132 days of gestation AVP projections were more or less equally distributed between the lamina of the ME, whereas in the adult AVP fibres are directed mainly to the internal lamina. The early appearance of AVP relative to CRF is consistent with the proposal that AVP may be a significant factor controlling adrenocorticotrophin release in the ovine fetus prior to 105 days of gestatio

ISSN:0028-3835    

DOI:10.1159/000124860

出版商:S. Karger AG    

年代:1987

数据来源: Karger

摘要:

It has been recently demonstrated that luteinizing hormone-releasing hormone (LHRH) can inhibit LHRH release by the hypothalamus, suggesting an ultrashort feedback of LHRH on LHRH neurons. In order to test this hypothesis, immunocytochemical localization of LHRH was conducted in the preoptic area of the rat brain. Contacts between endings and neuronal cell bodies staining for LHRH were observed. This direct interaction between LHRH neurons might be well the morphological basis for an autoregulation of the LHRH system in the rat brain.

ISSN:0028-3835    

DOI:10.1159/000124861

出版商:S. Karger AG    

年代:1987

数据来源: Karger

ISSN:0028-3835    

DOI:10.1159/000124862

出版商:S. Karger AG    

年代:1987

数据来源: Karger