Uptake and release of tryptophan and serotonin: an HPLC method to study the flux of endogenous 5-hydroxyindoles through synaptosomes.
An HPLC assay with fluorometric detection has been developed that is sensitive enough to measure simultaneously endogenous levels of tryptophan, serotonin (5-hydroxytryptamine, or 5-HT), and 5-hydroxyindoleacetic acid (5-HIAA) inside synaptosomes as well as that released into the incubation medium. Using this assay, we have observed that tryptophan is rapidly taken up by synaptosomes and turned over to 5-HIAA without a concurrent release of 5-HT. Exogenous 5-HT is also rapidly taken up, and, within 20-30 min, 80% of the 5-HT is deaminated. Veratridine induces release of both tryptophan and 5-HT from synaptosomes. Changes in the disposition of exogenous tryptophan or 5-HT can be completely accounted for by uptake or by stoichiometric changes in metabolites. This assay method should be valuable in the study of 5-HT pools and in the determination of from which pool 5-HT release occurs.
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D000818:Animals; D001921:Brain / Q000187:drug effects / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D005473:Fluoxetine / Q000494:pharmacology; D006897:Hydroxyindoleacetic Acid / Q000378:metabolism; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D012701:Serotonin / Q000378:metabolism*; D013574:Synaptosomes / Q000187:drug effects / Q000378:metabolism*; D014364:Tryptophan / Q000378:metabolism*; D014701:Veratridine / Q000494:pharmacology
D005473:Fluoxetine; D012701:Serotonin; D006897:Hydroxyindoleacetic Acid; D014701:Veratridine; D014364:Tryptophan