Effects of L-tryptophan and other amino acids on electroencephalographic sleep in the rat

Brain Res. 1990 Oct 1;528(2):300-7. doi: 10.1016/0006-8993(90)91671-3.


Electroencephalographic sleep was quantitated in adult male Sprague-Dawley rats following single injections of the methylesters of tryptophan, valine or alanine. The amino acids were administered at the onset of the daily light period (09.00 h); electrographic data were collected for the succeeding 6-h period. Saline served as the injection control, and fluoxetine, a serotonin-reuptake blocker, as a positive control. The injection of tryptophan methylester (125 mg/kg) caused a delay in rapid eye movement (REM) sleep onset, and significantly reduced the amount of REM sleep during the first 2 h postinjection. Tryptophan produced no effect on sleep onset, nor did it influence total sleep time. Fluoxetine (2.5 mg/kg) produced similar effects, as previously observed. The methylesters of valine and alanine were without effect on REM sleep, when injected at a molar dose equivalent to that for tryptophan. No consistent effects of any of the test substances were noted on non-REM (NREM) sleep or waking time, or on any of the other sleep indices quantitated. Together, the data indicate that tryptophan selectively reduces REM sleep; the effect is not due to a non-specific action of amino acids or their methylesters. The effect on REM sleep may be the consequence of a tryptophan-induced stimulation of 5-HT synthesis and release, since it is like that produced by fluoxetine, a drug that enhances transmission across serotonin synapses.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Alanine / pharmacology*
  • Animals
  • Computers
  • Electroencephalography / drug effects*
  • Fluoxetine / pharmacology
  • Male
  • Rats
  • Rats, Inbred Strains
  • Sleep / drug effects*
  • Tryptophan / pharmacology*
  • Valine / pharmacology*


  • Fluoxetine
  • Tryptophan
  • Valine
  • Alanine