Plasma prolactin changes following fenfluramine in depressed patients compared to controls: an evaluation of central serotonergic responsivity in depression.

In an attempt to evaluate the responsiveness of the serotonergic neurotransmitter system in depression, fenfluramine, a serotonin releasing agent, was administered to 18 depressed patients and 10 controls, and placebo was administered to 16 of the depressed patients in a double-blind paradigm. Plasma prolactin levels were measured prior to and for five hours following fenfluramine. Fenfluramine produced a significant increase in prolactin in both patients and controls. However, the prolactin response to fenfluramine whether measured as an absolute increase or percent increase from baseline was significantly less in depressed patients than controls. This difference remained equally statistically significant when age-and-sex-matched pairs of depressed patients and controls were compared. These results suggest that the central serotonergic system is less responsive in depressed patients than controls.