The hyperphagic effect of nociceptin/orphanin FQ in rats.

Nociceptin/orphanin FQ (NC), the endogenous ligand of the opioid receptor-l ike 1 (ORL1) receptor, has been reported to stimulate feeding in rats. The present article reviews the studies so far published on the effect of NC on food intake and reports new findings concerning the sensitivity of brain r egions to the hyperphagic effect of NC in rats. The results obtained indica te that the hypothalamic arcuate nucleus is the most sensitive site among t he brain regions so far investigated. On the basis of these findings and of the neurochemical and electrophysiological effects of NC, possible mechani sms of action and possible interactions with other neurotransmitter systems affecting feeding are discussed. (C) 2000 Elsevier Science Inc. All rights reserved.