This study evaluated the effect of peripheral injections of a beta3 adrenergic agonist, BRL-37,344 on food intake and whether this inhibition could be blocked by a nonspecific beta-adrenergic antagonist, propranolol, given peripherally or into the central nervous system. When BRL-37,344 was injected intraperitoneally (i.p.) into lean and obese Zucker rats, food intake was decreased. The reduction of food intake by BRL-37,344 was attenuated when propranolol was administered i.p. prior to giving the beta adrenergic agonist. When propranolol was administered into the third cerebral ventricle, it increased food intake in lean rats, but not the fatty rats. Propranolol administered into the third cerebral ventricle attenuated the effect on food intake of i.p. injection of BRL-37,344. These studies support the hypothesis that there are peripheral beta-3 adrenergic receptors that can reduce food intake and that there are central beta2 or beta3 adrenergic receptors that mediate the peripheral effect of the beta3 agonist.