Hypothalamus

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

Ventromedial preoptic prostaglandin E2 activates fever-producing autonomic pathways.

Abstract: Fever is thought to be initiated by pyrogenic cytokines inducing the production of prostaglandin E2 (PGE2) in the preoptic area (POA); PGE2 may act as a paracrine mediator that stimulates the neural pathways that raise body temperature. This essential role for prostaglandins in fever first was proposed 25 years ago, but the specific preoptic cell groups at which PGE2 acts and the pathways through which fever is produced remain poorly understood. To better define the role of preoptic PGE2 in fever, we developed a new method for combining acute brain injections with Fos immunohistochemistry. We microinjected a threshold dose of PGE2 to construct an anatomically detailed map of fever-producing preoptic sites. The most pyrogenic preoptic sites were clustered along the ventromedial aspect of the POA, surrounding and just anterior to the organum vasculosum of the lamina terminalis. We then used Fos immunohistochemistry to identify the pattern of neural activation induced by fever-producing preoptic injections of PGE2 and compared it with the Fos pattern seen after systemic immune stimulation. PGE2 fever was accompanied by Fos induction in the ventromedial POA and the parvicellular subnuclei of the paraventricular nucleus of the hypothalamus (PVH). In contrast to the Fos pattern seen after intravenous lipopolysaccharide administration, PGE2 injection did not induce Fos in the circumventricular organs or the magnocellular subnuclei of the PVH. These observations establish a potential site of PGE2 action during fever and help define candidate pathways through which fever occurs.

Sex differences in the distribution of androgen receptors in the human hypothalamus.

Abstract: The present study reports for the first time the distribution of androgen receptor immunoreactivity (AR-ir) in the human hypothalamus of ten human subjects (five men and five women) ranging in age between 20 years and 39 years using the antibody PG21. Prolonged postmortem delay (72:00 hours) or fixation time (100 days) did not influence the AR-ir. In men, intense nuclear AR-ir was found in neurons of the horizontal limb of the diagonal band of Broca, in neurons of the lateromamillary nucleus (LMN), and in the medial mamillary nucleus (MMN). An intermediate nuclear staining was found in the diagonal band of Broca, sexually dimorphic nucleus of the preoptic area, paraventricular nucleus, suprachiasmatic nucleus, ventromedial nucleus, and infundibular nucleus, whereas weaker labeling was found in the bed nucleus of the stria terminalis, medial preoptic area, dorsal and ventral zones of the periventricular nucleus, supraoptic nucleus, and nucleus basalis of Meynert. In most brain areas, women revealed less staining than men. In the LMN and the MMN, a strong sex difference was found. Cytoplasmic labeling was observed in neurons of both sexes, although women showed a higher variability in the intensity of such staining. However, no sex differences in AR-ir were observed in the bed nucleus of the stria terminalis, the nucleus basalis of Meynert, or the islands of Calleja. Species differences and similarities of the AR-ir distribution are discussed. The present results suggest the participation of androgens in the regulation of various hypothalamic processes that are sexually dimorphic.

Characterization of the Neuroanatomical Distribution of Agouti-Related Protein Immunoreactivity in the Rhesus Monkey and the Rat

Abstract: Agouti-related protein (AGRP) is a recently described homolog of the skin agouti protein. AGRP is transcribed primarily in the adrenal and hypothalamus and is a high affinity antagonist of the neural melanocortin-3 and melanocortin-4 receptors. The perikarya expressing AGRP messenger RNA are found in the arcuate nucleus of the rat and rhesus monkey. Using a polyclonal antibody against the pharmacologically active domain of AGRP (amino acids 83-132), we have also characterized the distribution of AGRP-immunoreactive neurons in both species. The major fiber tracts are conserved in both species, with dense projections originating in the arcuate nucleus and proceeding along the third ventricle. Dense fiber bundles are also visible in the paraventricular, dorsomedial, and posterior nuclei in the hypothalamus, in the bed nucleus of the stria terminalis, and in the lateral septal nucleus of the septal region. AGRP-containing neurons are not visualized in a number of areas, including portions of the amygdala, thalamus, and brain stem, that express MC3-R and MC4-R messenger RNA and receive innervation from POMC neurons that serve as the source of melanocortin agonists. Thus, AGRP is most likely to be involved in modulating a conserved subset of the physiological functions of central melanocortin peptides. Based on the particular distribution of AGRP neurons, those functions are likely to include the central control of energy homeostasis.

In vivo metabolic activity of a putative circadian oscillator, the rat suprachiasmatic nucleus.

Abstract: The suprachiasmatic nucleus (SCN) has been proposed as a site for an endogenous circadian oscillator in mammals, since lesions of the nucleus abolish a wide spectrum of overt-circadian rhythms. To demonstrate that a directly measurable property of the SCN itself in intact (unlesioned) animals is affected by environmental light and exhibits circadian rhythmicity, we used the autoradiographic 2-deoxy-D-[14C]glucose method to determine glucose utilization of rat SCN under a variety of lighting conditions. Our experiments indicate an important role for the SCN in circadian rhythm organization, and we believe the deoxyglucose method will prove useful as a tool for better understanding the functions and mechanisms of circadian clocks. Key words: suprachiasmatic nucleus, circadian rhythm, 2-deoxy-D-[14C]glucose.