Melatonin counteracts the 5-aminolevulinic acid-induced rise of rat forebrain tryptophan and serotonin concentrations at night

S. Daya, K. O. Nonaka, R. J. Reiter

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When rats were exposed to extended light into the normal dark phase, the administration of 5-aminolevulinic acid (5-ALA) markedly stimulated the accumulation of tryptophan (TRP) and the synthesis of serotonin (5-HT) in the forebrain. When a single injection of melatonin (25 μg) was given near the end of the 5-ALA treatment, the rise in forebrain TRP levels was either totally prevented or reversed; likewise, the increased levels of 5-HT were also suppressed. Melatonin by itself also slightly suppressed forebrain TRP levels in non-5-ALA-treated rats. Whether these are pharmacological or physiological effects of melatonin remains to be determined.

Original languageEnglish (US)
Pages (from-to)113-116
Number of pages4
JournalNeuroscience Letters
Issue number1
StatePublished - Jun 22 1990



  • 5-Aminolevulinic acid
  • Melatonin
  • Serotonin
  • Tryptophan

ASJC Scopus subject areas

  • Neuroscience(all)

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