Differential effects of melanocortin peptides on ingestive behaviour in rats: evidence against the involvement of MC3 receptor in the regulation of food intake

The pro-opiomelanocortin-derived peptides decrease food intake possibly vi a MC4 receptor. In this study we compared the effects of alpha-melanocyte-s timulating hormone (MSH), beta-MSH and gamma(1)-MSH (0.2, 1.0 and 5.0 mu g, i.c.v.) on food intake. alpha-MSH and beta-MSH inhibited spontaneous food intake in a dose dependent manner, whereas the gamma(1)-MSH did not. alpha- MSH and beta-MSH but not gamma(1)-MSH tall 5.0 mu g, i.c.v. inhibited fasti ng-induced food intake about 50%. None of the three peptides inhibited flui d consumption in water-deprived (24 h) rats. It is suggested that MC, recep tor, activated selectively by gamma(1)-MSH, is not involved in the regulati on of food intake. (C) 2000 Elsevier Science Ireland Ltd. All rights reserv ed.