Response of neuropeptide Y-induced feeding to μ-, δ- and κ-opioid receptor antagonists in the neonatal chick

It is known that opioid antagonists reduce the orexigenic effect of neropeptide Y (NPY) in mammals. We studied the effect of three opioid antagonists oil NPY-induced feeding in male broiler chicks. beta-Funaltrexamine (beta-FNA). naloxonazine (NAL). ICI- 174,864 (ICI) or nor-binaltorphimine (nor-BNI), antagonists of mu-, mu(i)-, delta- or kappa-receptors, and NPY were co-injected in chicks. Food intake was measured 30 min after treatment. Co-injection of beta-FNA or NAL was effective in reducing NPY-induced feeding. whereas ICI and nor-BNI had little effect on NPY-induced feeding. These data suggest that the mu-opioid receptor, especially the tj-opioid has some relation to NPY-induced feeding, and implies that ail endogenous ligand, Such as beta-endorphin, participates in the orexigenic effect of NPY in neonatal chicks. (C) 2004 Elsevier Ireland Ltd. All rights reserved.