title: Effect of valine on 5-HT-mediated prolactin release in healthy volunteers, and on mood in remitted depressed patients.
abstract: BACKGROUND
  Animal experimental studies suggest that the amino acid valine may decrease brain serotonin (5-HT) function by inhibiting the transport of the 5-HT precursor, L-tryptophan, across the blood barrier. The aim of the present study was to assess whether valine could decrease brain 5-HT function in healthy subjects and provoke symptomatic relapse in recently remitted depressed patients taking antidepressant drug treatment.
  
  
  METHODS
  We studied the effect of valine (30 g) on the prolactin (PRL) response to the 5-HT releasing agent, D-fenfluramine, in healthy male subjects and on the mood of 12 remitted depressed patients taking either selective serotonin re-uptake inhibitors (n = 10) or lithium and amitriptyline (n = 2).
  
  
  RESULTS
  Valine significantly lowered the PRL response to D-fenfluramine in healthy subjects. In the remitted depressives, valine caused a mild but detectable lowering of mood on a number of measures but only one patient experienced a significant relapse in mood.
  
  
  CONCLUSIONS
  Valine administration may decrease brain 5-HT neurotransmission in humans. This effect could explain the mild increase in depressive symptoms in patients taking 5-HT-potentiating drugs.
authors.affiliation: Psychopharmacology Research Unit, Littlemore Hospital, Oxford.
authors.forename: D J
authors.initials: DJ
authors.lastname: Williamson
authors.forename: S F
authors.initials: SF
authors.lastname: McTavish
authors.forename: S B
authors.initials: SB
authors.lastname: Park
authors.forename: P J
authors.initials: PJ
authors.lastname: Cowen
mesh_terms: D000328:Adult; D000339:Affect / Q000187:drug effects* / Q000502:physiology; D000368:Aged; D000597:Amino Acids, Branched-Chain / Q000097:blood; D000639:Amitriptyline / Q000627:therapeutic use; D000928:Antidepressive Agents / Q000627:therapeutic use; D001812:Blood-Brain Barrier / Q000187:drug effects / Q000502:physiology; D018592:Cross-Over Studies; D003866:Depressive Disorder / Q000188:drug therapy / Q000503:physiopathology* / Q000523:psychology; D004311:Double-Blind Method; D004359:Drug Therapy, Combination; D005260:Female; D005277:Fenfluramine; D006801:Humans; D008094:Lithium / Q000627:therapeutic use; D008297:Male; D008875:Middle Aged; D010555:Personality Inventory; D011388:Prolactin / Q000097:blood*; D012008:Recurrence; D012016:Reference Values; D012701:Serotonin / Q000502:physiology*; D017367:Selective Serotonin Reuptake Inhibitors / Q000627:therapeutic use; D014364:Tryptophan / Q000097:blood; D014633:Valine / Q000494:pharmacology*
chemical_list: D000597:Amino Acids, Branched-Chain; D000639:Amitriptyline; D000928:Antidepressive Agents; D005277:Fenfluramine; D008094:Lithium; D011388:Prolactin; D012701:Serotonin; D017367:Selective Serotonin Reuptake Inhibitors; D014364:Tryptophan; D014633:Valine