American Journal of Clinical Nutrition, Vol 24, 1053-1059, Copyright © 1971 by The American Society for Clinical Nutrition, Inc.

Plasma amino acids in schizophrenic patients with methionine or cysteine loading and a monoamine oxidase inhibitor

¹ From the Thudichum Psychiatric Research Laboratory, Galesburg State Research Hospital, Galesburg, Illinois 61401

The plasma amino acid levels in four male chronic schizophrenic patients were determined during: a control period, loading with dl-methionine (in three patients only), and then in turn with l-cysteine, tranylcypromine, tranylcypromine plus l-cysteine, and 15 days after the final loading period. The administration of dl-methionine and of l-cysteine markedly increased the total amino acid levels in the blood of the three patients who had received dl-methionine. Tranylcypromine alone did not affect the amino acid levels. When tranylcypromine was given with l-cysteine, an increase in the total amino acid concentration occurred in all four patients, but was slight in the patient who had not received dl-methionine. Therefore, the continued striking elevations observed in the three patients receiving dl-methionine were attributed chiefly to the greater toxicity of dl-methionine as compared with that of l-cysteine. A temporal relationship between behavioral worsening and high total amino acid levels was noted, but exacerbation of psychotic symptoms correlated better with the appearance of urinary psychotomimetic N-dimethyltryptamines (7, 13, 15, 16).