NPY receptors and opioidergic system are involved in NPY-induced feeding in goldfish

The present study evaluated the effects of both intraperitoneal (i.p.) and intracerebroventricular administration of selective Y-1 [(Leu(31), Pro(34))-NPY] and Y-2[(Pro(13), Tyr(36))-NPY (13-36)] receptor agonists on food intake in satiated goldfish. Food intake (FI) was significantly increased by central administration of the Y-1 agonist (1 mug), but not by the Y-2 agonist, at 2 h postinjection. The feeding increase induced by (Leu(31), Pro(34))-NPY was in a similar magnitude to that obtained after ICV injection of the neuropeptide Y, and both feeding stimulations were reversed by the NPY (27-36), a general NPY antagonist. The i.p. administration of the agonists either did not significantly modify (Y, agonist) or decreased (Y-1 agonist) food intake in goldfish. These data indicate that it is the Y-1-like (similar to Y-1 and/or Y-5) receptor, and not Y-2, that is involved in the central modulation of the feeding behavior in goldfish. We also investigated the possible involvement of opioid peptides as: mediators of the NPY stimulatory action on food intake in goldfish. The ICV administration of naloxone (10 mug), a general opioid antagonist, blocked the NPY-induced feeding in goldfish, suggesting that the opioidergic system is involved in feeding regulation by NPY. (C) 2000 Published by Elsevier Science Inc.