The effect of norbinaltorphimine, beta-funaltrexamine and naltrindole on NPY-induced feeding.

The non-selective opioid receptor antagonist naloxone decreases the robust feeding observed after i.c.v. injection of neuropeptide Y (NPY). In the present study we evaluated the effects of three selective opioid receptor antagonists on NPY-induced feeding. Graded doses of norbinaltorphimine (norBNI), beta-funaltrexamine (beta-FNA) and naltrindole (NTI), antagonists of the kappa, mu and delta receptors respectively, were preinjected (i.c.v.) in male rats prior to injection of 5 micrograms NPY (i.c.v.). Food intake was measured 1, 2 and 4 h post-NPY injection. Injection of beta-FNA and norBNI were most effective in reducing NPY-induced feeding, whereas NTI had little effect on NPY-induced feeding.