Abstract

Central injections of dopamine (DA) or epinephrine (EPI) have been found to suppress feeding behavior in hungry rats. In the present study, 24 different brain areas, in 299 animals, were examined to localize the precise region of catecholamine (CA) sensitivity. Essentially all sites outside the hypothalamus, as well as in the medial portion of the hypothalamus, were relatively or totally unresponsive to DA or EPI. The area of greatest sensitivity for both agonists (where they yielded a 50--70% suppression of feeding) was found to be the perifornical region of the lateral hypothalamus, extending from the caudal aspect of the paraventricular nucleus to the caudal aspect of the ventromedial nucleus. Dorsal, lateral, or ventrolateral movement of the injection site away from the fornix and into the zona incerta or the lateral hypothalamic medial forebrain bundle area caused a dramatic reduction in the effectiveness of the CA. These findings are consistent with histochemical studies, which have shown the fornix to be surrounded by CA varicosities, and pharmacological studies, which have shown the perifornical region to be most sensitive to the anorexic effect of centrally injected amphetamine, which releases endogenous CA. It is suggested that the perifornical hypothalamus plays a role in the process of inhibiting food consumption in response to increased dopaminergic and adrenergic activity.