Functional meaning of tryptophan-induced increase of 5-HT metabolism as clarified by in vivo voltammetry

Maria Grazia De Simoni, Andrzej Sokola, Fabio Fodritto, Giuseppe Dal Toso, Sergio Algeri

Research output: Contribution to journalArticlepeer-review


Differential pulse voltammetry with carbon fiber electrodes was used to study serotonin (5-HT) metabolism in freely moving rats. The electrodes implanted in the striatum recorded the extracellular 5-hydroxyindoleacetic acid (5-HIAA) oxidation peak after oral tryptophan (150 mg/kg). This 5-HT precursor did not modify the 5-HIAA peak in any rat tested, but it raised 5-HIAA levels determined in total tissue by a classical biochemical method (HPLC). The administration of 5-hydroxytryptophan (5-HTP) (25 mg/kg i.p.) induced an increase of 5-HIAA detectable both in the extracellular medium by voltammetry and in tissue samples. As previously shown, dorsal raphe electrical stimulation raises extracellular 5-HIAA in the striatum and this effect is enhanced by pretreatment with tryptophan. The results suggest that tryptophan in 'normal' conditions enhances 5-HT metabolism without affecting 5-HT release unless such release is stimulated. 5-HTP increases 5-HT metabolism and release.

Original languageEnglish
Pages (from-to)89-94
Number of pages6
JournalBrain Research
Issue number1
Publication statusPublished - May 12 1987


  • High-pressure liquid chromatography (HPLC)
  • In vivo voltammetry
  • Serotonin metabolism
  • Truptophan

ASJC Scopus subject areas

  • Developmental Biology
  • Molecular Biology
  • Clinical Neurology
  • Neuroscience(all)

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