EFFECTS OF DOPAMINERGIC AGONISTS AND ANTAGONISTS ON FEEDING IN INTACT AND 6-HYDROXYDOPAMINE-TREATED RATS

Abstract

The effects on food intake of treatments which alter central dopaminergic function were examined in rats. Doses of d-amphetamine that increased the conversion of 3H-tyrosine to 3H-dopamine in the brain decreased food intake, an effect that was reduced by the systemic administration of the dopaminergic antagonists .alpha.-methyltyrosine, haloperidol or spiroperidol. The dopaminergic agonists, apomorphine, dopa, cocaine and methylphenidate, also reduced feeding and these effects were attenuated by low doses of spiroperidol. In larger doses, spiroperidol decreased feeding, and this effect was potentiated by .alpha.-methyltyrosine. The ability of dopaminergic agonists and antagonists to inhibit food intake was also observed in rats treated with 6-hydroxydopamine so as to produce a selective 83% depletion of dopamine. In these animals, d-amphetamine was less effective as an anorexic agent; dopa, apomorphine, .alpha.-methyltyrosine and spiroperidol were more effective in reducing food intake. These alterations in sensitivity may reflect neurochemical changes which occur at residual dopaminergic synapses after subtotal lesions of dopaminergic neurons. Increases and decreases in central dopaminergic activity can reduce feeding and some intermediate rate of dopamine release may provide an optimal level of neuronal activity for feeding by the hungry animal.