Effects of the 5-hydroxytryptamine agonist D,L-fenfluramine on energy balance in rats: influence of gender.

The effect of the 5-hydroxytryptamine agonist D,L-fenfluramine on energy balance was investigated in male and female rats in order to detect a possible gender difference. Male and female rats, either gonadally intact or castrated, received a daily injection of the 5-hydroxytryptamine (5HT) agonist fenfluramine during 28 days. Body weight and food intake were monitored throughout the treatment period. At the end of the treatment, rats were decapitated and their carcasses were processed in order to determine the carcass contents of energy, fat and protein. Regardless of the gender of the rats, fenfluramine significantly delayed the gains in body weight, body energy and body fat in either castrated or gonadally intact rats. In female rats, castration accelerated body weight gain in rats injected with saline as well as in those treated with fenfluramine. Additionally, castrated female rats deposited more energy, fat and protein than gonadally intact rats. In contrast, castrated male rats, independently of whether they received saline or fenfluramine, gained less body weight and deposited less energy, fat and protein than non-castrated male rats. In conclusion, the results of this study show that D,L-fenfluramine is as effective in altering energy balance in male as it is in female rats.