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Specificity of the tryptophan depletion method.
T Klaassen1, W J Riedel, N E Deutz
1European Graduate School for Neurosciences, Maastricht University, The Netherlands.
Psychopharmacology
|February 23, 1999
Summary
Tryptophan depletion specifically impacts mood and memory, unlike lysine depletion. This suggests tryptophan
Area of Science:
- Neuroscience
- Biochemistry
- Psychology
Background:
- Tryptophan depletion is known to induce psychological changes.
- The specificity of these effects requires further investigation.
Purpose of the Study:
- To determine if the psychological effects of tryptophan depletion are specific to tryptophan or a general amino acid depletion effect.
- To investigate the impact of tryptophan depletion on mood and memory performance.
Main Methods:
- Double-blind, placebo-controlled crossover study with 13 healthy subjects.
- Administration of amino acid mixtures with or without tryptophan (TRP) or lysine (LYS).
- Measurement of plasma amino acid levels, mood, tiredness, and memory performance 6 hours post-ingestion.
Main Results:
- Tryptophan depletion significantly decreased plasma TRP levels by 77% and induced more tiredness, lower mood, and declined memory performance compared to placebo.
- Lysine depletion significantly decreased plasma LYS levels by 51% but did not result in significant changes in mood or memory compared to placebo.
- The observed psychological effects were specific to tryptophan depletion.
Conclusions:
- The psychological effects of tryptophan depletion are specific to tryptophan itself and not a general consequence of amino acid depletion.
- These findings support the hypothesis that tryptophan depletion specifically affects brain serotonin metabolism.
- The study highlights the role of tryptophan in modulating mood and cognitive functions.