The influence of intravenous L-tryptophan on plasma melatonin and sleep in men

Pharmacopsychiatry. 1991 Jan;24(1):17-20. doi: 10.1055/s-2007-1014427.


The sleep-inducing mechanisms of L-Tryptophan (L-Trp) are generally thought to be mediated by a central serotonergic activation. Evidence is presented that some effects of L-Trp on sleep may be mediated by melatonin, a Trp-metabolite with sedative properties. Trp effects on vigilance, sleep, and plasma-melatonin concentrations were measured after double-blind application of 0, 1, 3, and 5 g L-Trp in nine and five healthy probands during daytime and nighttime, respectively. A significant sleep-inducing effect was observed after L-Trp administration during daytime and nighttime. The infusions of L-Trp caused a massive elevation of plasma melatonin levels. This effect was significant both during the night and the day, indicating that the increment of circulating melatonin may be of extrapineal origin.

Publication types

  • Clinical Trial
  • Controlled Clinical Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Dose-Response Relationship, Drug
  • Humans
  • Infusions, Intravenous
  • Male
  • Melatonin / blood*
  • Radioimmunoassay
  • Sleep / drug effects*
  • Tryptophan / administration & dosage
  • Tryptophan / pharmacology*


  • Tryptophan
  • Melatonin