Analysis of feeding suppression produced by perifornical hypothalamic injection of catecholamines, amphetamines and mazindol

Abstract

The effects on feeding of perifornical hypothalamic injection of catecholamines, amphetamines and mazindol were examined in hungry rats. In pargyline-pretreated subjects, both dopamine and epinephrine significantly suppressed food intake, at doses as low as 31 ng for dopamine and 150 ng for epinephrine (the latter injected with an alpha-adrenoceptor blocker). This effect was reliably strengthened by inhibiting catecholamine deamination or presynaptic catecholamine uptake. Perifornical injections of amphetamine, mazindol, methamphetamine, and phenmetrazine also suppressed feeding. The magnitude of this effect in individual animals was positively correlated with the effect produced by catecholamine agonists. Moreover, this effect of mazindol was partially antagonized by perifornical injection of dopaminergic and beta-adrenoceptor blockers. The effects of amphetamine and epinephrine were abolished by these drugs, while dopamine's effect was selectively inhibited by the dopaminergic antagonist. Serotonergic antagonists produced no change. These findings lend support to the hypothesis that perifornical hypothalamic catecholamine neurons, through dopaminergic receptors and beta-adrenoceptors, are involved in inhibiting feeding behavior, as well as in mediating the anorexic action of the amphetamines and mazindol.