Lithium restores abnormal platelet 5-HT transport in patients with affective disorders.

Kinetic analysis of the transport of 5-HT into the blood platelets of depressed patients and recovered depressive patients has shown that the rate of accumulation of 5-hydroxytryptamine (5-HT) is significantly decreased both before and after recovery from the illness. This abnormality is corrected by both short and long-term lithium treatment. As a corollary to these studies, the effect of lithium in vitro on 5-HT uptake has been studied and the results are opposite to those reported in vivo. These findings suggest that lithium acts indirectly, and possible mechanisms of its action are discussed.