Muscimol, a GABA agonist, or beta-endorphin, an endogenous opiate receptor agonist, stimulated food intake in satiated rats when injected into the ventromedial hypothalamus. A similar effect was elicited by norepinephrine. Eating induced by muscimol was inhibited by bicuculline but not by naltrexone or phentolamine. In contrast, norepinephrine-induced eating was terminated by both phentolamine and bicuculline, whereas beta-endorphin-induced eating was blocked by both naltrexone and bicuculline. These observations implicate GABA in the regulation of food intake and suggest that this putative transmitter may be involved also in the increased food intake induced by norepinephrine or opiate receptor agonists.

Stimulation of food intake by muscimol and beta endorphin