Effects of desipramine and fluvoxamine treatment on the prolactin response to tryptophan. Serotonergic function and the mechanism of antidepressant action

Abstract

It has been hypothesized that enhancement of brain serotoninergic (5-HT) function is involved in the mechanism of action of some antidepressants. To test this, the prolactin response to intravenously administered tryptophan, a clinical measurement of 5-HT function, was assessed before and during antidepressant treatment. Depressed patients received the tricyclic desipramine hydrochloride (N = 24) or the 5-HT reuptake inhibitor fluvoxamine maleate (N = 30). The prolactin response was significantly enhanced after long-term treatment (4 weeks) but not as reliably increased after short-term (1-week) desipramine treatment. Fluvoxamine enhanced the prolactin response after both short- and long-term treatment. Enhancement of the prolactin response was not clearly correlated with clinical improvement. The results of this study are consistent with preclinical evidence of enhanced 5-HT function during treatment with these classes of antidepressants, but also indicate that enhanced 5-HT function is not a sufficient condition for antidepressant efficacy.