NALOXONE REDUCES THE FEEDING EVOKED BY INTRACEREBROVENTRICULAR GALANIN INJECTION

Central injection of galanin elicits feeding in satiated rats. We rece ntly observed galanin-immunoreactive fibers in synaptic connection wit h a population of beta-endorphin-immunopositive cell bodies and dendri tes in the basal hypothalamus. Because beta-endorphin also stimulates food intake, these morphological findings raised the possibility that stimulation of feeding by galanin may, in part, be mediated by beta-en dorphin release. First, we observed that ICV injection of galanin (1.5 -6.0 nmol) stimulated feeding in a dose-related fashion. Next, the eff ect on food intake of the opioid receptor antagonist naloxone (20-200 mu g, ICV) administered immediately preceding galanin (3 nmol, ICV) wa s evaluated. Galanin-induced feeding was suppressed by naloxone in a d ose-dependent manner with a maximal suppression of 76% at the highest naloxone dose. These findings support the existence of a functional li nk between galanin and beta-endorphin and are in accord with the view that stimulation of food intake by galanin may, in part, be mediated b y increased beta-endorphin release.