Serotonin in the raphe nuclei: Regulation by light and an endogenous pacemaker

F. R A Cagampang, S. Yamazaki, Y. Otori, S. T. Inouye

Research output: Contribution to journalArticlepeer-review

64 Scopus citations


Temporal changes of serotonin (5-HT) content in the median (MRN) and dorsal (DRN) raphe nuclei were measured in rats kept under various lighting conditions. Serotonin content in the MRN and DRN under light-dark (LD) condition showed diurnal rhythmicity, with a peak during early light phase and a trough during the dark phase. In constant dark (DD) condition, a single peak was observed and was out of phase to the 5-HT peak found under LD condition. Animals exposed to constant light (LL) after 2 days in DD showed marked increase in 5-HT after lights on. These results suggest that changes in 5-HT in the MRN and DRN are regulated by an endogenous pacemaker and by light.

Original languageEnglish (US)
Pages (from-to)49-52
Number of pages4
Issue number1
StatePublished - Oct 1993


  • Circadian rhythm
  • HPLC
  • Raphe nuclei
  • Rat
  • Serotonin

ASJC Scopus subject areas

  • Neuroscience(all)


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