Comparison of 50- and 100-g L-tryptophan depletion and loading formulations for altering 5-HT synthesis: Pharmacokinetics, side effects, and mood states

Donald M. Dougherty, Dawn M. Marsh-Richard, Charles W. Mathias, Ashley J. Hood, Merideth A. Addicott, F. Gerard Moeller, Christopher J. Morgan, Abdulla A.B. Badawy

Research output: Contribution to journalArticlepeer-review

26 Scopus citations

Abstract

Rationale: Differences in 5-hydroxytryptamine (5-HT) function have been the subject of extensive research in psychiatric studies. Many studies have manipulated l-tryptophan (Trp) levels to temporarily decrease (depletion) or increase (loading) 5-HT synthesis. While most researchers have used a 100-g formulation, there has been ongoing interest in using smaller-sized formulations. Objectives: This study examined the time course of multiple plasma indicators of brain 5-HT synthesis after a 50-g depletion and loading as a comparison to the corresponding 100-g formulations that are typically used. Materials and methods: Plasma was collected from 112 healthy adults at seven hourly intervals after consumption of either a 50- or 100-g depletion or loading. Self-ratings of mood and somatic symptoms were completed before and after Trp manipulations. Results: The primary findings were that (1) the 50- and 100-g formulations produced the expected changes in plasma indicators after both depletion (-89% and -96%, respectively) and loading (+570% and +372%, respectively); (2) the 100-g depletion showed more robust effects at the 4, 5, and 6 h measurements than the 50-g depletion; (3) there was significant attrition after both the 100-g depletion and loading, but not after either of the 50-g formulations; and (4) both the 50- and 100-g depletions produced increases in negative self-ratings of mood and somatic symptoms, while loading significantly increased negative ratings after the 100 g only. Conclusions: There are important considerations when choosing among formulation sizes for use in Trp manipulation studies, and the complete 7-h time-course data set of the typical plasma Trp measures presented here may help researchers decide which methodology best suits their needs.

Original languageEnglish (US)
Pages (from-to)431-445
Number of pages15
JournalPsychopharmacology
Volume198
Issue number3
DOIs
StatePublished - Jun 1 2008

Keywords

  • Competing amino acids
  • Depletion
  • Human
  • L-Tryptophan
  • Mood
  • Serotonin
  • Side effects
  • Time course

ASJC Scopus subject areas

  • Pharmacology

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