Dissociation of the anorexic effects of fenfluramine and amphetamine following intrahypothalamic injection.

Injections of amphetamine and fenfluramine directly into the hypothalamus produced changes in food intake dependent upon the site of injection. No significant modulation occurred following injections into the ventromedial nucleus. In the lateral hypothalamus both drugs gave rise to an overall depression of feeding behaviour but the time-course of action for the drugs differed and there was a high negative correlation between the action of the two drugs within individual animals. These findings provide further evidence for the belief that fenfluramine and amphetamine exert their anorexic actions through the lateral hypothalamus rather than the ventromedial nucleus, but suggest that different chemical mechanisms are involved in the anorexia produced by each drug.