Effect of electroconvulsive therapy (ECT) on plasma tryptophan

The concentrations of total and free plasma tryptophan were measured in 12 unipolar depressed patients before and after a course of electroconvulsive therapy (ECT) and before and after single ECTs during the course of treatment. Eleven patients undergoing diagnostic cystoscopy served and controls to examine the acute effect of anaesthesia. Total and free plasma tryptophan concentrations in the depressed patients were not significantly different from control values and were not changed by course of ECT. Free plasma tryptophan varied considerably within individual patients. Total plasma tryptophan was reduced acutely by ECT/anaesthesia in the depressed patients (P less than 0.05) and by anaesthesia in the cystoscopy controls (P less than 0.01). Free plasma tryptophan was not significantly altered. This reduction in total plasma tryptophan could be secondary to an effect of thiopentone on albumin binding of tryptophan.