title: Impaired recognition of fear facial expressions in 5-HTTLPR S-polymorphism carriers following tryptophan depletion.
abstract: BACKGROUND
  Genotype at the 5' promoter region (5-HTTLPR) of the serotonin transporter has been implicated in moderating the effects of acute tryptophan depletion on neurocognitive functioning. Acute tryptophan depletion has been associated with the processing of fear-relevant cues, such as emotional expressions, but the effect of genotype at the 5-HTTLPR has not been assessed.
  
  
  OBJECTIVE
  The present study investigated the effects of acute tryptophan depletion on the recognition of standardized facial expressions of emotions in healthy volunteers classified as ll homozygotes or s carriers.
  
  
  METHODS
  A double-blind between-groups design was used with volunteers randomly selected to ingest capsules containing an amino acid mixture specifically lacking tryptophan, or placebo capsules containing lactose. 5 h after capsule ingestion, subjects were required to identify anger, disgust, fear, happiness, sadness, and surprise expressions that progressed from neutral to each full emotional expression in 5% steps.
  
  
  RESULTS
  Tryptophan depletion significantly impaired the recognition of fearful facial expressions in s carriers but not ll homozygotes. This impairment was specific to fear expressions. No significant differences in the recognition of other expressions were found. Free tryptophan levels were correlated with fear recognition in s carriers but not ll homozygotes.
  
  
  CONCLUSIONS
  The effects of acute tryptophan depletion on the processing of emotional expressions varies as a function of genotype at the 5-HTTLPR. Depletion impairs the recognition of fear in s carriers but not ll homozygotes. This finding reinforces the importance of considering genotype when assessing the behavioral effects of pharmacologic modulation.
authors.affiliation: Mood and Anxiety Program, National Institute of Mental Health,National Institutes of Health, Bethesda, MD 20892, USA. amarsh@post.harvard.edu
authors.forename: Abigail A
authors.initials: AA
authors.lastname: Marsh
authors.forename: Elizabeth C
authors.initials: EC
authors.lastname: Finger
authors.forename: Beata
authors.initials: B
authors.lastname: Buzas
authors.forename: Niveen
authors.initials: N
authors.lastname: Soliman
authors.forename: Rebecca A
authors.initials: RA
authors.lastname: Richell
authors.forename: Meena
authors.initials: M
authors.lastname: Vythilingham
authors.forename: Daniel S
authors.initials: DS
authors.lastname: Pine
authors.forename: David
authors.initials: D
authors.lastname: Goldman
authors.forename: R J R
authors.initials: RJ
authors.lastname: Blair
mesh_terms: D000328:Adult; D003072:Cognition Disorders / Q000523:psychology*; D004311:Double-Blind Method; D005149:Facial Expression; D005239:Fear / Q000502:physiology / Q000523:psychology; D005260:Female; D006801:Humans; D008297:Male; D011110:Polymorphism, Genetic; D021641:Recognition, Psychology; D050486:Serotonin Plasma Membrane Transport Proteins / Q000235:genetics*; D014364:Tryptophan / Q000172:deficiency*
chemical_list: C493230:SLC6A4 protein, human; D050486:Serotonin Plasma Membrane Transport Proteins; D014364:Tryptophan