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

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Bibliographic Details
Title:	Comparison of 50- and 100-g l-tryptophan depletion and loading formulations for altering 5-HT synthesis: pharmacokinetics, side effects, and mood states.
Authors:	Dougherty, Donald, Marsh-Richard, Dawn, Mathias, Charles, Hood, Ashley, Addicott, Merideth, Moeller, F., Morgan, Christopher, Badawy, Abdulla
Source:	Psychopharmacology. Jun2008, Vol. 198 Issue 3, p431-445. 15p. 3 Charts, 2 Graphs.
Subjects:	Serotonin, Drug side effects, Mood (Psychology), Tryptophan, Physiology
Abstract:	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. 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. 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. 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. 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. [ABSTRACT FROM AUTHOR]
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Database:	Psychology and Behavioral Sciences Collection

Description
Abstract:	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. 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. 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. 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. 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. [ABSTRACT FROM AUTHOR]
ISSN:	00333158
DOI:	10.1007/s00213-008-1163-2