• Evidence suggests that lithium treatment alters serotoninergic (5-HT) function in laboratory animals and humans. Since 5-HT function may be abnormal in patients with affective disorders, we studied 23 such patients by measuring responses to intravenous infusion of the 5-HT precursor tryptophan before and during short-term (less than one week) or long-term (greater than three weeks) lithium treatment. The prolactin response to tryptophan was significantly enhanced after short-term lithium treatment; long-term lithium treatment had no effect. Other studies have shown that the prolactin response to tryptophan is also enhanced after long-term tricyclic antidepressant treatment in depressed patients and after short- and long-term lithium treatment in healthy subjects. The present findings suggest that lithium treatment enhances 5-HT function, but that homeostatic responses of the 5-HT system to long-term lithium treatment may differ in patients with affective disorder and healthy subjects.
Price LH, Charney DS, Delgado PL, Heninger GR. Lithium Treatment and Serotoninergic FunctionNeuroendocrine and Behavioral Responses to Intravenous Tryptophan in Affective Disorder. Arch Gen Psychiatry. 1989;46(1):13-19. doi:10.1001/archpsyc.1989.01810010015002