Hypothalamus

About: Hypothalamus is a research topic. Over the lifetime, 22301 publications have been published within this topic receiving 1085925 citations.

Estradiol upregulates Bcl-2 expression in adult brain neurons.

Abstract: Bcl-2, a protein which negatively modulates apoptosis, is up-regulated by estrogen in several tissues To determine the effect of estradiol on Bcl-2 in the adult brain, its immunoreactive distribution was examined in the hypothalamic arcuate nucleus of female rats under different endocrine conditions The number of Bcl-2-immunoreactive neurons was significantly increased (p < 0001) on the day of estrus compared with proestrus, diestrus and metestrus, was decreased by ovariectomy and showed a dose-response increase after estradiol administration to ovariectomized rats Progesterone, when injected simultaneously with estradiol, reduced the effect of estradiol These findings indicate that ovarian hormones regulate Bcl-2 in hypothalamic neurons and suggest that this protein may be involved in the neuroprotective effects of estrogen

Do gonadotropin-releasing hormone, tyrosine hydroxylase-, and beta-endorphin-immunoreactive neurons contain estrogen receptors? A double-label immunocytochemical study in the Suffolk ewe

Abstract: We used double label immunocytochemistry to examine the brains of ovariectomized ewes and determine whether GnRH, tyrosine hydroxylase-(TH), and beta-endorphin-immunoreactive (IR) neurons contain IR-estrogen receptors (ER) Because of their possible importance as a target for the feedback actions of estradiol, we also examined the presence of nuclear ER in LH-IR cells of the pars tuberalis of the pituitary Although preoptic GnRH neurons were frequently in close proximity to ER-IR cells, only one out of approximately 1000 GnRH cells examined was found to coexpress ER In contrast, in the arcuate nucleus and vicinity, 3-5% of TH cells and 15-20% of beta-endorphin cells contained ER Virtually all LH-IR cells, seen predominantly in the ventral portion of the pars tuberalis, coexpressed ER These results suggest that in sheep as in rodents, the influence of estradiol on the reproductive neuroendocrine system is not directly mediated by GnRH neurons, but instead is conveyed to GnRH cells via presynaptic affer

Effect on various putative neurotransmitters on the secretion of corticotrophin-releasing hormone from the rat hypothalamus in vitro-a model of the neurotransmitters involved.

Abstract: The effect of incubating the hypothalamus of adult male rats with various neurotransmitters upon the release of corticotrophin-releasing hormone (CRH) was studied. The CRH activity in the incubation medium was assayed in 48 h median eminence-lesioned rats and the corticosteroidogenesis of excised adrenals in vitro was used as the end-point. 5-Hydroxytryptamine (100 pg/ml-10ng/ml) caused a dose-dependent release of CRH which was antagonized by methysergide (30-100 ng/ml). The response to 5-hydroxytryptamine was also inhibited by hexamethonium and atropine which indicated that it was acting through a cholinergic interneurone. Melatonin (10 ng) did not alter the basal release of CRH but inhibited the action of both 5-hydroxytryptamine (10 ng) and acetylcholine (3 pg). Thus it appears that both 5-hydroxytryptamine and melatonin play a role in the control of CRH release. Noradrenaline blocked the release of CRH induced by both acetylcholine and 5-hydroxytryptamine and presumably this inhibition was caused by direct action on the CRH neurone. gamma-Aminobutyric acid (GABA) also inhibited the release of CRH and may also be involved in the regulation of CRH secretion. The inhibitory neurotransmitters, noradrenaline, GABA and melatonin, act via independent receptor mechanisms. A model based on the above data is presented.