Neuropeptide Y and catecholamine-mediated neuronal transmission in mechanisms of feeding-behaviour induction.

Intracerebroventricular administration of various doses of neuropeptide Y (NPY) to rats had different effects on their feeding behaviour: the lowest dose (100 ng) decreased food intake, but higher doses (5 micrograms) markedly increased the intake. Prazosin, a selective blocker of alpha 1-adrenergic receptors, suppressed the effect induced by 5 micrograms (but not 100 ng) NPY. No such effect was observed with injections of yohimbine or propranolol. The opiate receptor antagonist, naloxone, blocked the feeding behaviour induced by 5 micrograms NPY without having any other effects on the responses induced by 100 ng NPY. The data obtained testify to heterogeneity within the NPY receptors of the central nervous system. It is concluded that the effects of high doses of NPY on feeding behaviour are mediated, at least in part, by alpha 1-adrenergic receptors.