alpha-melanocyte stimulating hormone prevents fasting-induced suppression of corticotropin-releasing hormone gene expression in the rat hypothalamic paraventricular nucleus

During fasting, corticotropin releasing hormone (CRH) mRNA decreases in the hypothalamic paraventricular nucleus (PVN), but the mechanism by which thi s takes place is not well understood. To test the hypothesis that the melan ocortin system may be involved in the regulation of CRH mRNA in the PVN dur ing fasting, the effect of intracerebroventricularly administered alpha-mel anocyte stimulating hormone (MSH) on CRH mRNA in the PVN was studied in fas ted animals by in situ hybridization histochemistry. Whereas fasting suppre ssed CRH mRNA levels in the PVN, alpha-MSH at doses of 150 and 300 ng every 6 h for 64 h prevented the fasting-induced suppression of CRH gene express ion in the PVN. These data indicate that the suppression of alpha-MSH synth esis may be responsible for the decreased CRH gene expression in the PVN du ring fasting. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.