Lack of effect of tryptophan depletion on the loudness dependency of auditory event related potentials in healthy volunteers

• Published in: Biological psychology Vol. 65; no. 2; pp. 137 - 145
• Main Authors: Massey, A.E, Marsh, V.R, McAllister-Williams, R.H
• Format: Journal Article
• Language: English
• Published: Shannon Elsevier B.V 2004; Elsevier Science
• Subjects: 5-HT; Acoustics; Adolescent; Adult; Auditory evoked potentials; Behavioral psychophysiology; Biological and medical sciences; Cross-Over Studies; Double-Blind Method; Electrophysiology; Evoked Potentials, Auditory - physiology; Female; Fundamental and applied biological sciences. Psychology; Humans; Male; Psychology. Psychoanalysis. Psychiatry; Psychology. Psychophysiology; Serotonin - metabolism; Serotonin - pharmacology; Tryptophan - deficiency; Tryptophan - pharmacology; Tryptophan depletion; 5-HT; Auditory evoked potentials; Tryptophan depletion; Human; Loudness; Psychotropic; Tryptophan; Hypnotic; Cognition; Electrodiagnosis; Depletion; Acoustic stimulus; Serotoninergic pathway; Aminoacid; Auditory evoked potential; Information processing; Antidepressant agent
• ISSN: 0301-0511; 1873-6246
• DOI: 10.1016/j.biopsycho.2003.03.001

It has previously been suggested that auditory event related potentials (AEPs) are a potential marker of central serotonergic (5-HT) activity in man, with the slope of the AEP amplitude stimulus intensity function (ASF-slope) inversely correlating with 5-HT activity. However, two recent studies investigating this hypothesis in healthy subjects by rapidly lowering central 5-HT concentrations using the acute tryptophan depletion paradigm have found no effect on ASF-slope [Biological Psychology, 59 (2002) 121; Psychopharmacology (Berl), 146 (1999) 101]. These studies employed a 50
g tryptophan depletion drink, which has been argued may not lower central 5-HT concentrations sufficiently. We here report the effect of tryptophan depletion on the AEP ASF-slope using 100
g amino acid drinks with and without tryptophan in 14 healthy male subjects, employing a within subject, double blind, random, balanced order, cross-over design. No significant effect of tryptophan depletion was found on ASF-slope. These negative findings cast further doubt on the hypothesis that the ASF-slope is an indicator of central 5-HT function.