Hypothalamus

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

Leptin activates neurons in ventrobasal hypothalamus and brainstem

Abstract: Leptin is a circulating protein secreted by adipocytes which has profound feeding, metabolic, and neuroendocrine effects. Leptin receptors have been localized to the hypothalamus, but the anatomic sites responsible for mediating the effects of circulating leptin have not been demonstrated. We report that systemic administration of leptin activates nuclear groups in the ventrobasal hypothalamus, including the ventromedial, dorsomedial, and ventral premammillary hypothalamic nuclei. Leptin also activated the parvicellular subdivisions of the paraventricular hypothalamic nucleus that project to parasympathetic and sympathetic preganglionic neurons. Finally, leptin administration activated the superior lateral parabrachial subnucleus, a nuclear group containing cholecystokinin neurons that project to the ventrobasal hypothalamus. These findings indicate that circulating leptin activates specific nuclear groups in the hypothalamus and brainstem known to regulate complex physiological responses during times of substrate availability.

Distribution and regulation of aromatase activity in the rat hypothalamus and limbic system.

Abstract: Conversion of androgen to estrogen in the rat brain is catalyzed by aromatase enzymes. The maximum concentrations of these enzymes are found within the hypothalamus and amygdala, where they appear to play an important role in the process by which androgens affect both behavior and neuroendocrine function. In the present study, we measured the levels of aromatase activity (AA) in 20 nuclei and brain regions of the adult rat brain. Individual nuclei were microdissected from 600-micron frozen sections. Tissues from 3 animals were pooled, and AA was measured by an in vitro radiometric assay that quantifies the stereospecific production of 3H2O from [1 beta-3H]androstenedione as an index of estrogen formation. We report that AA is heterogeneously distributed within the rat brain. The greatest amounts of activity were found in the bed nucleus (n.) of the stria terminalis (700 protein fmol/h . mg) and in the medial (MA) and cortical amygdala (400-600 fmol/h . mg protein) of the male. There was an evident rostral-caudal and medial-lateral gradient in AA throughout the diencephalon. Activity was high in the periventricular preoptic n. and medial preoptic n.; intermediate in the suprachiasmatic preoptic n., anterior hypothalamus, periventricular anterior hypothalamus, and ventromedial n.; and low in the arcuate n.-median eminence, lateral preoptic n., supraoptic n., dorsomedial n., and lateral hypothalamus. Regions devoid of measurable AA included the medial and lateral septum, caudate-putamen, hippocampus, and parietal cortex. In the female, AA was greatest in the MA and cortical amygdala. We found that AA in the MA, stria terminalis n., suprachiasmatic preoptic n., periventricular preoptic in., medial preoptic n., anterior hypothalamus, and ventromedial n. was significantly greater (P less than 0.05) in males than in females. Orchidectomy reduced AA to levels seen in females, and administration of testosterone to castrated males restored AA in these areas. No significant sex differences were observed in any other hypothalamic or amygdaloid nuclei, although AA was increased by testosterone treatment in the periventricular anterior hypothalamus, arcuate n.-median eminence, and lateral hypothalamus. Our results provide a quantitative profile of AA in specific hypothalamic and limbic nuclei of the rat brain as well as information on the control of AA within these discrete regions.

Eating or Drinking Elicited by Direct Adrenergic or Cholinergic Stimulation of Hypothalamus

Abstract: A double cannula system, allowing repeated stimulation of central structures with crystalline chemicals, was developed. This technique was employed to study the effects of adrenergic and cholinergic stimulation of the lateral hypothalamus of rats. Drug-specific effects on the feeding and drinking mechanisms, respectively, were observed.

Two sexually dimorphic cell groups in the human brain

Abstract: A quantitative analysis of the volume of 4 cell groups in the preoptic- anterior hypothalamic area (PO-AHA) and of the supraoptic nucleus (SON) of the human brain was performed in 22 age-matched male and female individuals. We suggest the term Interstitial Nuclei of the Anterior Hypothalamus (INAH 1–4) to identify these 4 previously undescribed cell groups in the PO-AHA. While 2 INAH and the SON were not sexually dimorphic, gender-related differences were found in the other 2 cell groups. One nucleus (INAH-3) was 2.8 times larger in the male brain than in the female brain irrespective of age. The other cell group (INAH-2) was twice as large in the male brain, but also appeared to be related in women to circulating steroid hormone levels. Since the PO- AHA influences gonadotropin secretion, maternal behavior, and sexual behavior in several mammalian species, these results suggest that functional sex differences in the hypothalamus may be related to sex differences in neural structure.

CNS Region-Specific Oxytocin Receptor Expression: Importance in Regulation of Anxiety and Sex Behavior

Abstract: The oxytocin receptor (OTR) is differentially expressed in the CNS. Because there are multiple mechanisms by which the OTR can be transcriptionally induced, we hypothesized that differences in OTR expression may be explained by activation of distinct signal transduction pathways and may be critical for the control of anxiety and sex behaviors. To determine the regulation and functional significance of this expression, we infused female rats with modifiers of protein kinases before assaying for behavior and oxytocin receptor binding. In the ventromedial nucleus of the hypothalamus (VMH), estrogen-dependent induction of oxytocin receptors required protein kinase C activation, and oxytocin infused here promoted female sex behavior but had no effect on anxiety. In contrast, dopamine controlled tonic oxytocin receptor expression in the central nucleus of the amygdala (cAmyg) through activation of protein kinase A, and oxytocin infused here was anxiolytic but had no effect on female sex behavior. Therefore, we have identified brain region-specific regulation of the OTR in the VMH and cAmyg. Distinct signal transduction pathways regulating receptor expression and binding in each brain region may mediate in part the ability of oxytocin to exert these differential behavioral effects.