In vivo microdialysis measures of extracellular serotonin in the rat hippocampus during sleep-wakefulness

Brain Res. 1999 Jul 3;833(2):291-6. doi: 10.1016/s0006-8993(99)01511-5.


We investigated extracellular 5-hydroxytryptamine (5-HT) levels in rat hippocampus during different stages of the sleep-waking cycle using in vivo microdialysis. The extracellular 5-HT level was highest in active waking (AW) and, when compared to AW, 5-HT level was progressively lower in quiet waking (QW; 78%), quiet sleep (QS; 50%) and REM (which we termed active sleep (AS); 40%). Functional implications of AS related-decreased 5-HT in the hippocampus are discussed.

Publication types

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

MeSH terms

  • Animals
  • Extracellular Space / metabolism
  • Hippocampus / metabolism*
  • Male
  • Microdialysis
  • Rats
  • Rats, Sprague-Dawley
  • Serotonin / metabolism*
  • Sleep, REM / physiology*
  • Wakefulness / physiology*


  • Serotonin