• 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.
Price LH, Charney DS, Delgado PL, Anderson GM, Heninger GR. Effects of Desipramine and Fluvoxamine Treatment on the Prolactin Response to Tryptophan: Serotonergic Function and the Mechanism of Antidepressant Action. Arch Gen Psychiatry. 1989;46(7):625–631. doi:10.1001/archpsyc.1989.01810070051009
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