Effect of electroconvulsive therapy on biopterin and large neutral amino acids in severe, medication-resistant depression

Biopterin. neopterin and the large neutral amino acids (LNAA), i.e. phenyla lanine, tyrosine, tryptophan, isoleucine, leucine and valine were measured in plasma of 20 severely depressed inpatients before and after a course of electroconvulsive therapy (ECT). These patients showed a significantly lowe r plasma biopterin concentration at baseline in comparison with healthy con trols. After treatment an increase in biopterin was found, which was statis tically significant in the depressed patients with psychotic features. The plasma phenylalanine-tyrosine ratio, which previously increased, normalised after ECT. Mean tryptophan concentration was lower in depressed patients t han in normal controls. The patients who responded to ECT showed an increas e in the tryptophan concentration and its ratio (tryptophan/LNAA) after tre atment. Our results suggest that ECT increases biopterin, which probably re sults in synthesis of amino acids, especially tyrosine. Furthermore, ECT se ems to increase cerebral tryptophan availability because of less tryptophan catabolism parallel with biopterin activation. More research is required t o see if biopterin could be useful as a biological marker for the depressiv e state in this subgroup of patients, because this compound seems to play a n important role in the etiology and treatment of depression. (C) 2001 Else vier Science Ireland Ltd. All rights reserved.