The effect of iproniazid and imipramine on the blood platelet 5-hydroxytrptamine level in man.

Observations are reported on the blood platelet 5-hydroxytryptamine content of six patients receiving imipramine, N-(gamma-dimethylaminopropyl)-iminodibenzyl hydrochloride. The response was a fall to a level of one-sixth of the original in three weeks, with little change thereafter. This is in sharp contrast to the action of iproniazid which caused a rise of some 200% in the blood platelet 5-hydroxytryptamine level over the same period. Imipramine in a concentration of 1 mg./ml. had no inhibitory action on 5-hydroxytryptophan decarboxylase; 8.0 mug./ml. of imipramine suppressed two-thirds of the in vitro uptake of 5-hydroxytryptamine (2.5 mug./ml.) by normal human platelets.