Fenfluramine and 5-hydroxytryptamine. Part 2: Involvement of brain 5-hydroxytryptamine in the anorectic activity of fenfluramine.

As it is well-known, fenfluramine produces anorexia and decrease in brain 5-hydroxytryptamine (5-HT). As it has been suggested that the anorectic effect of fenfluramine may be due to a release of brain 5-HT, we have examined the influence of several drugs active on 5-HT mechanisms and metabolism, on the anorexigenic activity of fenfluramine. These studies were made in relationship with the depletion of 5-HT levels and the concentration of brain fenfluramine or m-trifluoromethyl-isopropylamine. The results have confirmed the involvement of a tryptaminergic mechanism in fenfluramine anorexia and suggest the hypothesis that fenfluramine itself can interfere with the serotoninergic system in the brain (stimulation of tryptaminergic neurons directly).