l-Dopa feeding suppression: Effect on catecholamine neurons of the perifornical lateral hypothalamus

Abstract

Injection of l-Dopa (0.8–200 nmoles) into the perifornical hypothalamus produced a dose-dependent suppression of feeding in hungry rats. This effect was positively correlated in magnitude with the same effect produced by the catecholamine agonists dopamine and epinephrine, and by the catecholamine-releasing drug amphetamine. l-Dopa's action was partially antagonized by separate injections of the dopaminergic blocker haloperidol (58% blockade) and the β-adrenergic blocker propranolol (38% blockade). Combined injections of these two antagonists produced a 90% blockade of l-Dopa's effect. Perifornical administration of the dopa decarboxylase inhibitors Ro 4-4602 and MK-486 was also shown to reverse l-Dopa's feeding suppression, at doses that enhanced the effect of injected dopamine and epinephrine. On the basis of these findings, l-Dopa appears to suppress food consumption in part through increased catecholamine synthesis, specifically within dopaminergic and adrenergic neurons of the perifornical hypothalamic region.