title: Differential effects of tri-allelic 5-HTTLPR polymorphisms in healthy subjects on mood and stress performance after tryptophan challenge.
abstract: Earlier data suggest that a polymorphism at the serotonin (5-HT) transporter gene (5-HTTLPR) may affect depression particularly in the face of stress due to interactions between 5-HT vulnerability and stress exposure. However, this interaction between 5-HT transporter-linked transcriptional promoter region (5-HTTLPR), 5-HT vulnerability and the affective effects of stress exposure has not yet been investigated. As participants with short-allele 5-HTTLPR genotypes may exhibit enhanced 5-HT vulnerability, this study examines the effects of tryptophan challenge on stress reactivity and performance in healthy participants with S'/S' vs L'/L' genotypes. Sixteen healthy subjects with homozygotic short alleles (S'/S'=S/L(G,) L(G)/L(G)) and 14 subjects with homozygotic long alleles (L'/L'=L(A)/L(A)) of the 5-HTTLPR were tested in a double-blind placebo-controlled design under acute stress exposure following tryptophan challenge or placebo. Although there were no 5-HTTLPR-related differences in stress responses, significant beneficial effects of tryptophan challenge on mood and stress performance were exclusively found in participants with S'/S' genotypes. These findings suggest greater brain 5-HT vulnerability to tryptophan manipulations in participants with S'/S' as compared with L'/L' 5-HTTLPR genotypes. This apparent genetic 5-HT vulnerability may become a meaningful risk factor for depression when brain 5-HT falls below functional need in the face of real severe stressful life events.
authors.affiliation: Faculty of Psychology and Neuroscience, Department of Neuropsychology and Psychopharmacology, University Maastricht, Maastricht, Netherlands. r.markus@psychology.unimaas.nl
authors.forename: C Rob
authors.initials: CR
authors.lastname: Markus
authors.forename: Christine
authors.initials: C
authors.lastname: Firk
mesh_terms: D000339:Affect / Q000187:drug effects*; D000483:Alleles; D018592:Cross-Over Studies; D005260:Female; D005838:Genotype; D006801:Humans; D006854:Hydrocortisone / Q000378:metabolism; D008297:Male; D011110:Polymorphism, Genetic; D011597:Psychomotor Performance / Q000187:drug effects; D012463:Saliva / Q000378:metabolism; D050486:Serotonin Plasma Membrane Transport Proteins / Q000235:genetics*; D013312:Stress, Physiological / Q000187:drug effects / Q000235:genetics*; D013315:Stress, Psychological / Q000235:genetics* / Q000378:metabolism; D014364:Tryptophan / Q000494:pharmacology*; D055815:Young Adult
chemical_list: C493230:SLC6A4 protein, human; D050486:Serotonin Plasma Membrane Transport Proteins; D014364:Tryptophan; D006854:Hydrocortisone