The appetite suppressant, d-fenfluramine, decreases self-stimulation at a feeding site in the lateral hypothalamus.

In prior studies rats showed a relative shift from self-stimulation to escape (i.e., from reward to aversion) following a large meal, obesity or anorectic doses of insulin. Racemic fenfluramine, on the other hand, decreased both self-stimulation and escape suggesting it had a general behavior suppressant property. To avoid the depressive, antidopaminergic effects of the l-isomer, this study tested the d-isomer which is primarily serotonergic. Rats were screened for stimulation-induced feeding and then trained to self-stimulate with one lever in 5-min periods that alternated with 5-min periods of automatic stimulation from which the animal could escape with a different lever. d-Fenfluramine (1.5-4.5 mg/kg IP) caused a dose-related decrease in self-stimulation. Stimulation-escape was relatively unaffected. This is interpreted as a decrease in feeding reward due to d-fenfluramine.