The central melanocortin system regulates food intake in goldfish

Posttranscriptional processing of proopiomelanocortin (POMC) yields melanocortin peptides, which are involved in the regulation of energy balance in mammals. The sequence preservation of the main brain melanocortin, a-melanocyte-stimulating hormone (alpha-MSH), suggests a conserved function throughout vertebrate evolution. We studied the involvement of the central melanocortin system. in the control of food intake in the goldfish. In situ hybridization studies done following molecular cloning of POW mRNA demonstrated positive POW mRNA cell bodies exclusively expressed within the mediobasal hypothalamus, in the anterior, posterior and inferior part of the lateral tuberal nucleus and the medial region of the lateral recess nucleus. POW expression is localized in brain areas appropriate for involvement in food intake and neuroendocrine regulation. Progressive fasting did not affect POW mRNA expression levels. Intracerebroventricular administration of [Nle(4), D-Phe(7)]-alpha-MSH (NDP-alpha-MSH), a universal melanocortin agonist, within nanomolar range, dose-dependently inhibited food intake 2 h after treatment. The results show for the first time a functional melanocortin system in fishes that participates in central regulation of food intake. The conserved central expression pattern of POW mRNA and role of MSH peptides in physiological regulation of food intake suggests that melanocortin functions were gained early in vertebrate evolution. (C) 2003 Elsevier B.V. All rights reserved.