Effects of fenfluramine on food intake, body weight, gastric emptying and brain monoamines in Syrian hamsters.

In the first experiment, dose-inhibition and -time functions are documented for the anorectic effects of d,l-fenfluramine in Syrian hamsters (Mesocricetus auratus). A dose of 20 mg/kg (IP) inhibited feeding for at least 2-4 hr. In the second experiment, chronic treatment of hamsters housed either in running wheels (exercise) or standard (sedentary) conditions with d,l-fenfluramine (20 mg/kg) produced an attenuation of weight gain relative to vehicle-treated controls. However, there was no differential weight loss in the exercising drug-treated group. This result was also obtained using 10 mg/kg d-fenfluramine. In the third experiment, d,l-fenfluramine greatly inhibited gastric emptying of a test meal in hamsters. In the fourth experiment, hamsters were found to sustain only small and transient decreases in brain 5HT and 5HIAA levels after acute or chronic treatment with d,l-fenfluramine. These findings are compared and contrasted with the known effects of fenfluramine in rats. It is concluded that there may be species differences in the impact of fenfluramine on brain function, and that this may not be in any simple way related to the anorexigenic action of this drug.