Hypothalamic neuropeptides could mediate the anorectic effects of fenfluramine.

Oxytocin, vasopressin and corticotrophin releasing factor have anorectic properties when injected centrally. We studied the kinetics of these neuropeptides by injecting fenfluramine, a drug which reduces food intake, in Long Evans rats. The drug was injected daily through a double chronic cannula implanted above the paraventricular nucleus of the hypothalamus; the rats had free access to pure macronutrients. The rats lost weight during the treatment. Their total caloric intake decreased mostly because the carbohydrate intake decreased, while the protein intake increased slightly. The synthesis and release of brain oxytocin and vasopressin were increased and the release of corticotrophin releasing factor was stimulated. The neuropeptides could be involved in fenfluramine-triggered mechanisms.