IMPACT OF EXPERIMENTALLY-INDUCED SEROTONIN DEFICIENCY BY TRYPTOPHAN DEPLETION ON SLEEP EEG IN HEALTHY-SUBJECTS

The tryptophan depletion test is a research strategy to investigate th e functional consequences of decreasing the brain serotonin metabolism . Because serotonin is involved in sleep regulation and the regulation of affective states, toe studied the acute polysomnographic effects o f tryptophan depletion and expected to induce similar changes of sleep EEG as observed in depressed patients. A total of 12 healthy subjects (mean age 34 +/- 3 years) had eight polysomnograms, divided in two bl ocks of 4 consecutive nights. After one adaptation and 1 baseline nigh t, subjects received a low-protein diet on day 3 and 4 until midday. O n day 4 at 18.00 h, they drank an amino acid mixture either devoid of tryptophan or containing 2.3 g of tryptophan (placebo control) in rand omized and double-blind order, resulting in an 85% decrease (tryptopha n depletion) and a 144% increase (placebo control) of serum tryptophan at 22.00 h. After tryptophan depletion but not placebo, significant e ffects on sleep EEG were observed in terms of decreased non-rapid eye movement (non-REM) stage 2, increase of wake %, and of rapid eye movem ent (REM) density compared with baseline. REM latency was not altered, however the first and second REM period interval were significantly s horter after tryptophan depletion. This study underlines the impact of the serotonergic system on sleep maintenance and on REM sleep. (C) 19 98 American College of Neuropsychopharmacology. Published by Elsevier Science Inc.