The conversion of [3H]tryptophan to 5-[3H]hydroxytryptamine in mouse brain following depletion of phenylalanine and tyrosine

K. M. Johnson, R. R. Fritz, T. W. Vickroy

Research output: Contribution to journalArticle


Phenylalanine ammonia-lyase (PAL), an enzyme which converts phenylalanine (Phe) and tyrosine (Tyr) to trans-p-cinnamic acid and trans-p-coumaric acid, respectively, was administered to mice and its effect on the conversion of [3H]tryptophan to 5-[3H]HT in the brain was measured. Although PAL significantly depleted plasma Tyr, it has little or no effect on either brain Tyr or catecholamine concentrations. Endogenous brain tryptophan levels were significantly increased 2 h after PAL administration, brain 5-HT was dramatically increased 4 h following PAL and each returned to baseline levels by 8 h. This return to baseline was accompanied by a marked decrease in the fraction of tryptophan converted to 5-HT during a 20 min pulse period preceding death, suggesting the activation of a compensatory decrease in 5-HT synthesis in response to increased 5-HT concentration. These data suggest that PAL administration readily produces reversible alterations in 5-HT synthesis and that this may be a fruitful approach to studying brain 5-HT function.

Original languageEnglish (US)
Pages (from-to)1075-1081
Number of pages7
JournalJournal of Neurochemistry
Issue number5
StatePublished - 1979


ASJC Scopus subject areas

  • Biochemistry
  • Cellular and Molecular Neuroscience

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