Background. Abnormalities of brain serotonin (5-HT) transmission have been implicated in the pathophysiology of bulimia nervosa (BN), but no conclusive data have yet been provided. The purpose of this study was to assess 5-HT transmission via the measurement of the prolactin (PRL) response to the specific 5-HT releasing agent d-fenfluramine (d-FEN) in both patients with BN and comparison subjects.

Methods. According to a double-blind placebo-controlled design, plasma PRL response to d-FEN was measured in 14 drug-free bulimics and 14 matched healthy controls. In both patients and controls, eating-related psychopathology, depressive and obsessive–compulsive symptoms, and aggressiveness were measured by rating scales.

Results. Baseline plasma levels of PRL and 17β-oestradiol were significantly reduced in bulimic patients, whereas basal plasma levels of cortisol did not significantly differ from healthy controls. PRL response to d-FEN was not different between patients and controls as groups, but it was significantly blunted in bulimics with high frequency bingeing ([ges ]2 binge episodes per day; N=7) as compared to both those with low frequency bingeing ([les ]1 binge episode per day; N=7) and matched controls. A significant negative correlation emerged between the frequency of binge episodes and the hormone response to d-FEN. Moreover, although patients scored higher than healthy subjects on rating scales assessing depressive and obsessive–compulsive symptoms and aggressiveness, no significant correlation was found between these measures and the PRL response to d-FEN.

Conclusions. These results support the idea that serotonin transmission is impaired in bulimic patients with frequent binge episodes.