title: A diurnal rhythm of immunoreactive alpha-melanocyte-stimulating hormone in discrete regions of the rat brain.
abstract: A significant diurnal variation in alpha-melanocyte stimulating hormone (alpha-MSH) concentrations was observed in discrete regions of the rat brain. During the 12 h light: 12 h dark cycle, alpha-MSH concentrations in each case were highest during the light period and lowest during the dark period. At 09.00 h, 3 h after lights were turned on, the peak alpha-MSH concentration occurred in the median eminence, the arcuate and dorsomedial hypothalamic nuclei and the periventricular thalamic nucleus. The paraventricular and anterior hypothalamic nuclei had highest alpha-MSH concentrations at 13.00 h. In the medial preoptic nucleus, the peak alpha-MSH concentrations appeared at 17.00 h. These changes in alpha-MSH content may reflect an alpha-MSH role in circadian variations in behavioral and neuroendocrine processes.
mesh_terms: D000818:Animals; D002940:Circadian Rhythm; D007031:Hypothalamus / Q000032:analysis*; D007032:Hypothalamus, Anterior / Q000032:analysis; D007033:Hypothalamus, Middle / Q000032:analysis; D008297:Male; D008473:Median Eminence / Q000032:analysis; D009074:Melanocyte-Stimulating Hormones / Q000032:analysis*; D010286:Paraventricular Hypothalamic Nucleus / Q000032:analysis; D011301:Preoptic Area / Q000032:analysis; D051381:Rats; D013787:Thalamic Nuclei / Q000032:analysis*
chemical_list: D009074:Melanocyte-Stimulating Hormones