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 int
ake in satiated goldfish. Food intake (FI) was significantly increased by c
entral administration of the Y-1 agonist (1 mug), but not by the Y-2 agonis
t, 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 eit
her did not significantly modify (Y, agonist) or decreased (Y-1 agonist) fo
od 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 po
ssible involvement of opioid peptides as: mediators of the NPY stimulatory
action on food intake in goldfish. The ICV administration of naloxone (10 m
ug), a general opioid antagonist, blocked the NPY-induced feeding in goldfi
sh, suggesting that the opioidergic system is involved in feeding regulatio
n by NPY. (C) 2000 Published by Elsevier Science Inc.