Effects of acute tryptophan depletion on plasma and cerebrospinal fluid tryptophan and 5-hydroxyindoleacetic acid in normal volunteers.
Brain serotonin synthesis and metabolism (turnover), as indicated by CSF concentrations of 5-hydroxyindoleacetic acid (5-HIAA), may depend on plasma concentrations of the essential amino acid L-tryptophan (TRP). We investigated the biochemical effects of acute plasma TRP depletion (ATD) in normal volunteers undergoing a 36-h CSF collection via lumbar drain. Six subjects who were in good health were put on a low-TRP diet (160 mg/day) 24 h before lumbar puncture; this diet was continued for the first 22 h of the CSF collection. At hour 22, subjects ingested a TRP-deficient 15-amino acid drink shown previously to deplete plasma TRP. Total plasma TRP, free plasma TRP, and CSF TRP subsequently decreased 86.3, 86.5, and 92.3%, respectively. CSF 5-HIAA decreased by 32.8%. Plasma total and free TRP concentrations were both decreased at approximately 2 h following ingestion of the TRP-free amino acid drink and were lowest approximately 6 h after ATD; CSF TRP and 5-HIAA were decreased at 2.5 h and approximately 4 h after ATD, respectively. CSF TRP was lowest 8.0 h later. CSF 5-HIAA continued to decrease 14 h after the TRP-deficient amino acid drink was given.
Williams
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WA
National Institutes of Health, National Institute on Alcohol Abuse and Alcoholism, Laboratory of Clinical Studies, Bethesda, Maryland 20892, USA.
Shoaf
S E
SE
Hommer
D
D
Rawlings
R
R
Linnoila
M
M
D000328:Adult; D000437:Alcoholism / Q000378:metabolism; D000596:Amino Acids / Q000008:administration & dosage; D001921:Brain / Q000378:metabolism; D001923:Brain Chemistry / Q000187:drug effects / Q000502:physiology*; D004032:Diet; D005260:Female; D006801:Humans; D006897:Hydroxyindoleacetic Acid / Q000097:blood* / Q000134:cerebrospinal fluid*; D008297:Male; D008875:Middle Aged; D012701:Serotonin / Q000096:biosynthesis; D014364:Tryptophan / Q000097:blood* / Q000134:cerebrospinal fluid* / Q000172:deficiency
D000596:Amino Acids; D012701:Serotonin; D006897:Hydroxyindoleacetic Acid; D014364:Tryptophan