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Hypothalamus
About: Hypothalamus is a research topic. Over the lifetime, 22301 publications have been published within this topic receiving 1085925 citations.
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TL;DR: Differences in basal levels and regulation of ER mRNA could be a substrate for sex differences in ER concentrations in the hypothalamus of the rat, and further raise the possibility ofsex differences in concentrations of nuclear proteins related to the control of ER gene expression.
Abstract: Previously, we showed that estrogen receptor (ER) messenger RNA (mRNA) levels are decreased in cells of the mediobasal hypothalamus of ovariectomized (OVX) female rats following an acute estradiol treatment. Here, we examined whether the level of ER mRNA remains depressed in the continued long-term presence of estradiol, and questioned if there is a systematic relationship between the concentration of estradiol and the decrease in ER mRNA level. OVX female rats were implanted for 2 weeks with silastic capsules containing various concentrations of estradiol. Tissue sections were hybridized with a [3H] single-stranded DNA probe prepared from the region of the rat ER complementary DNA corresponding to the steroid binding domain, and relative mRNA level was assessed by counting grains over cells in specific hypothalamic nuclei. Estradiol induced a dose-dependent decrease in ER mRNA levels. Message levels declined in the ventrolateral aspect of the ventromedial nucleus (VLVM) by 57% and in the arcuate nucleus ...
211 citations
TL;DR: The degree of maturation and the differentiation of hypothalamic astrocytesin vivo are correlated with the ability of neurons to sprout branches or spines in response to steroid hormones and may underlie regionally specific differences in synaptic patterning.
Abstract: One of the more striking sexual dimorphisms in the adult brain is the synaptic patterning in some hypothalamic nuclei In the arcuate nucleus (ARC) males have twice the number of axosomatic and one-half the number of axodendritic spine synapses as females The opposite pattern is observed in the immediately adjacent ventromedial nucleus (VMN) In both cases, early exposure to testosterone dictates adult dimorphism, but the exact timing, mechanism, and site of steroid action remain unknown Astrocytes also exhibit sexual dimorphisms, and their role in mediating neuronal morphology is becoming increasingly evident Using Golgi-Cox impregnation to examine neuronal morphology and glial fibrillary acidic protein immunoreactivity (GFAP-IR) to characterize astrocytic morphology, we compared structural differences in dendrites and astrocytes from the ARC and VMN in postnatal day 2 rat pups from four hormonally different groups Consistent with previous observations, testosterone exposure induced a rapid and dramatic stellation response in ARC astrocytes Coincident with this change in astrocytic morphology was a 37% reduction in the density of dendritic spines on ARC neurons In contrast, astrocytes in the VMN were poorly differentiated and did not respond to testosterone exposure, nor were there any changes in neuronal dendrite spine density However, VMN neurons exposed to testosterone had almost double the number of branches compared with that in controls These data suggest that the degree of maturation and the differentiation of hypothalamic astrocytes in vivo are correlated with the ability of neurons to sprout branches or spines in response to steroid hormones and may underlie regionally specific differences in synaptic patterning
210 citations
TL;DR: Combination of retrograde neuronal tracing procedures with the identification of Fos protein following discrete stimuli shows populations of neurons, projecting to the supraoptic nuclei, which are preferentially activated by intravenous infusion of either hypertonic saline or angiotensin II.
210 citations
TL;DR: It is concluded that within the first 4 h, hormonal and metabolic signals relay starvation-induced information to the hypothalamus and leptin secretion decreases before leptin mRNA or fat depot weight, showing synthesis-independent regulation.
Abstract: To identify the sequences of changes in putative signals, reception of these and responses to starvation, we sampled fed and starved rats at 2- to 6-h intervals after removal of food 2 h before dark. Metabolites, hormones, hypothalamic neuropeptide expression, fat depots, and leptin expression were measured. At 2 h, insulin decreased, and FFA and corticosterone (B) increased; by 4 h, leptin and glucose levels decreased. Neuropeptide Y messenger RNA (mRNA) increased 6 h after food removal and thereafter. Adrenal and plasma B did not follow ACTH and were elevated throughout, with a nadir at the dark-light transition. Leptin correlated inversely with adrenal B. Fat stores decreased during the last 12 h. Leptin mRNA in perirenal and sc fat peaked during the dark period, resembling plasma leptin in fed rats. We conclude that 1) within the first 4 h, hormonal and metabolic signals relay starvation-induced information to the hypothalamus; 2) hypothalamic neuropeptide synthesis responds rapidly to the altered metabolic signals; 3) catabolic activity quickly predominates, reinforced by elevated B, not driven by ACTH, but possibly to a minor extent by leptin, and more by adrenal neural activity; and 4) leptin secretion decreases before leptin mRNA or fat depot weight, showing synthesis-independent regulation. (Endocrinology 140: 4015‐ 4023, 1999)
210 citations
TL;DR: A pronounced innervation of the contralateral SCN was observed, of which the neurotransmitter remains to be established, and Pha‐L tracing indicated the existence of SCN projections which could not be ascribed to one of the presently investigated peptides.
Abstract: The efferent projections of the suprachiasmatic nucleus (SCN) in the golden hamster have been examined by using the anterograde tracer Phaseolus vulgaris leucoagglutinin (Pha-L). SCN projections were further localized through a combination of restricted SCN-lesions and immunocytochemistry for three well-known peptidergic transmitters contained in SCN neurons, viz. vasopressin (VP), vasoactive intestinal peptide (VIP), and gastrin-releasing peptide (GRP). Thus, major terminal fields of SCN-derived VP were detected in the medial preoptic nucleus, the anterior part of the paraventricular nucleus of the thalamus (PVA), the medial parvicellular part of the paraventricular nucleus of the hypothalamus (PVN), and the medial part of the dorsomedial nucleus of the hypothalamus (DMH). VIP-containing projections from the SCN were discovered in the PVA, anterior and dorsal parvicellular divisions of the PVN, subparaventricular area, and medial DMH. Efferent fibers from the SCN containing GRP were restricted to the subparaventricular area, medial DMH, and supraoptic nucleus. In addition, Pha-L tracing indicated the existence of SCN projections which could not be ascribed to one of the presently investigated peptides. Furthermore, a pronounced innervation of the contralateral SCN was observed, of which the neurotransmitter remains to be established. The results of the present study indicate that the different neuronal populations in the SCN, as characterized by their transmitter content, also show a clear diversity in their preferential target areas.
210 citations