Lithium increases 5-HT-mediated prolactin release.

The effects of short-term (3-4 days) lithium treatment on the prolactin responses to intravenous clomipramine (0.1 mg/kg), metoclopramide (5 micrograms/kg) and haloperidol (2.5-5 micrograms/kg) were assessed in male volunteers. Prolactin responses to clomipramine were significantly enhanced by lithium while those following administration of haloperidol and metoclopramide were not significantly altered. Lithium did not change the cortisol response to clomipramine. The results suggest that lithium may selectively enhance 5-HT mediated prolactin release. These data are consistent with the hypothesis that synergistic effects of lithium and clomipramine on brain 5-HT function may be involved in their therapeutic effect in resistant depression.