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April 1972

Effect of L-Tryptophan on Brain Serotonin Metabolism in Depressed Patients

Author Affiliations

Bethesda, Md
From the Section on Psychiatry, Laboratory of Clinical Science, National Institute of Mental Health, Bethesda, Md. Dr. Dunner is now at the New York State Psychiatric Institute, Columbia University, New York.

Arch Gen Psychiatry. 1972;26(4):364-366. doi:10.1001/archpsyc.1972.01750220074014

Cerebrospinal fluid 5-hydroxyindoleacetic acid (5-HIAA), the major metabolite of serotonin, was assayed in a group of five depressed patients before and during treatment with L-tryptophan, with and without probenecid. L-tryptophan administration was associated with a slight increase in the baseline levels of 5-HIAA, but caused a twofold to threefold increase in the accumulation of 5-HIAA in the cerebrospinal fluid following probenecid administration. The apparent increase in brain serotonin turnover produced by L-tryptophan in these patients was not accompanied by an improvement in depression.