Tryptophan depletion and aggressive responding in healthy males

• Published in: Psychopharmacology Vol. 126; no. 2; p. 97
• Main Authors: Moeller, F G, Dougherty, D M, Swann, A C, Collins, D, Davis, C M, Cherek, D R
• Format: Journal Article
• Language: English
• Published: Germany 01.07.1996
• Subjects: Adult; Aggression - drug effects; Aggression - physiology; Humans; Male; Tryptophan - blood; Tryptophan - pharmacology
• ISSN: 0033-3158
• DOI: 10.1007/BF02246343

In order to study the effect of decreasing plasma tryptophan levels on aggressive responding in a controlled laboratory setting, we administered two doses (25 g and 100 g) of a tryptophan-free amino acid mixture to ten healthy male subjects after 24 h of a low tryptophan diet. Subjects were screened for current or past psychiatric, or non-psychiatric medical illness. Aggressive responding on a free-operant laboratory measure of aggression (the Point Subtraction Aggression Paradigm) and plasma tryptophan levels were measured before and after drinking the amino acid mixture. There was a significant increase in aggressive responding 5 h after the 100 g mixture and a significant increase in aggressive responding 6 h after the 25 g mixture compared to a baseline day when no drink was administered. There was also a significant decrease in plasma tryptophan at 5 hours after ingestion compared to baseline for both doses of amino acid mixture. This study supports the hypothesis that tryptophan depletion increases aggressive responding in healthy males in a laboratory setting, probably by decreasing brain serotonin.