Influence of unilateral ECT on tryptophan metabolism in endogenous depression

Thirteen patients with endogenous depression received an oral load of L-tryptophan (100 mg/kg) before and after a series of unilateral ECT. Age-matched and sex-matched controls also received the tryptophan load twice, at intervals corresponding to those used in the patients. After the loads the level of tryptophan in serum was lower in patients than in control subjects. ECT failed to influence either baseline or postload tryptophan levels. The results are consistent with the notion of disturbances in tryptophan metabolism in patients with endogenous depression, but they fail to clarify the mechanism responsible for the antidepressant effect of ECT.