Hypothalamus

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

Central administration of glucagon-like peptide-1 activates hypothalamic neuroendocrine neurons in the rat.

Abstract: Within the central nervous system, glucagon-like peptide-1-(7–36) amide (GLP-1) acts as a transmitter, inhibiting feeding and drinking behavior. Hypothalamic neuroendocrine neurons are centrally involved in the regulatory mechanisms controlling these behaviors, and high densities of GLP-1 binding sites are present in the rat hypothalamus. In the present study we have, over a period of 4 h, followed the effect of centrally injected GLP-1 on plasma levels of the neurohypophysial hormones vasopressin and oxytocin. Plasma levels of corticosterone and glucose were also followed across time after central administration of GLP-1. In conscious, freely moving, and unstressed rats, central injection of GLP-1 significantly elevated plasma levels of vasopressin 15 and 30 min after administration (basal, 0.8 ± 0.2 pg/ml; 15 min, 7.5 ± 2.0 pg/ml; 30 min, 5.6 ± 1.1 pg/ml; mean ± sem) and elevated corticosterone 15 min after administration (52 ± 13 vs. 447 ± 108 ng/ml, basal vs. 15 min; mean ± sem). In contrast, plasma o...

Corticotropin-releasing factor: co-expression within distinct subsets of oxytocin-, vasopressin-, and neurotensin-immunoreactive neurons in the hypothalamus of the male rat.

Abstract: Two immunohistochemical methods that allow the concurrent localization of neuroactive substances within individual neurons have been used to identify, count, and chart the distribution of corticotropin-releasing factor (CRF)-immunoreactive cells in the paraventricular nucleus of the hypothalamus (PVH) that may also contain an additional peptide. In colchicine-treated male rats a moderate number of oxytocin-stained cells, localized primarily in a discrete, anterior part of the magnocellular division of the nucleus, was found also to stain positively for CRF. Similarly, oxytocin and CRF immunoreactivity were jointly expressed in magnocellular neurons distributed diffusely in the supraoptic nucleus. Smaller numbers of vasopressin- and neurotensin-stained neurons centered in specific parts of the parvocellular division of the PVH were stained with antisera against CRF. Possible mechanisms whereby the function of subsets of magnocellular and parvocellular neurosecretory neurons can be modulated differentially are discussed.

Stimulation of Human-Growth-Hormone Secretion by L-Dopa

Abstract: The effect of L-dopa, a precursor of Central-nervous-system catecholamines, on growth-hormone secretion was studied in a group of patients with Parkinson's disease undergoing treatment with the drug. Oral doses (0.5 g) caused a significant rise in plasma growth hormone in patients initially starting therapy or on chronic therapy for as long as 11 months. The rise in plasma growth hormone persisted for 120 minutes after the administration of the drug. The L-dopa-induced rise in plasma growth hormone could not be blocked by either oral or intravenous glucose administration. The data suggest that a dopaminergic mechanism in the median eminence or a norepinephrine-sensitive site in the hypothalamus or limbic system may be involved in the regulation of growth-hormone secretion. Furthermore, patients with Parkinson's disease, on L-dopa therapy, appear to be under the influence of elevated plasma growth hormone for a substantial part of the day.

Arcuate Glucagon-Like Peptide 1 Receptors Regulate Glucose Homeostasis but Not Food Intake

Abstract: OBJECTIVE— Glucagon-like peptide-1 (GLP-1) promotes glucose homeostasis through regulation of islet hormone secretion, as well as hepatic and gastric function. Because GLP-1 is also synthesized in the brain, where it regulates food intake, we hypothesized that the central GLP-1 system regulates glucose tolerance as well. RESEARCH DESIGN AND METHODS— We used glucose tolerance tests and hyperinsulinemic-euglycemic clamps to assess the role of the central GLP-1 system on glucose tolerance, insulin secretion, and hepatic and peripheral insulin sensitivity. Finally, in situ hybridization was used to examine colocalization of GLP-1 receptors with neuropeptide tyrosine and pro-opiomelanocortin neurons. RESULTS— We found that central, but not peripheral, administration of low doses of a GLP-1 receptor antagonist caused relative hyperglycemia during a glucose tolerance test, suggesting that activation of central GLP-1 receptors regulates key processes involved in the maintenance of glucose homeostasis. Central administration of GLP-1 augmented glucose-stimulated insulin secretion, and direct administration of GLP-1 into the arcuate, but not the paraventricular, nucleus of the hypothalamus reduced hepatic glucose production. Consistent with a role for GLP-1 receptors in the arcuate, GLP-1 receptor mRNA was found to be expressed in 68.1% of arcuate neurons that expressed pro-opiomelanocortin mRNA but was not significantly coexpressed with neuropeptide tyrosine. CONCLUSIONS— These data suggest that the arcuate GLP-1 receptors are a key component of the GLP-1 system for improving glucose homeostasis by regulating both insulin secretion and glucose production.