title: The regulation of 5-hydroxytryptamine release from superfused synaptosomes by 5-hydroxytryptamine and its immediate precursors.
abstract: The effect of L-tryptophan, 5-hydroxy-L-tryptophan (5-HTP), and 5-hydroxytryptamine (5-HT) on the K+-evoked release of [3H]5-HT from superfused rat brain synaptosomes was studied. 5-HT at concentrations above 10 nM significantly inhibited the K+-evoked release of [3H]5-HT. A slight enhancement of [3H]5-HT release was observed at a concentration of 5nM. In contrast tryptophan at a concentration of 10 nM significantly enhanced [3H]5-HT release with little effect at higher concentrations. 5-HTP did not significantly effect [3H]5-HT release. The results confirm previous findings that 5-HT inhibits its own release from nerve endings, and demonstrate that low concentrations of tryptophan in the synaptic region may act as a positive feedback regulator of 5-HT release.
mesh_terms: D006916:5-Hydroxytryptophan / Q000494:pharmacology*; D000818:Animals; D001921:Brain / Q000502:physiology*; D002997:Clomipramine / Q000494:pharmacology; D007700:Kinetics; D011188:Potassium / Q000494:pharmacology; D051381:Rats; D012701:Serotonin / Q000378:metabolism* / Q000494:pharmacology; D013574:Synaptosomes / Q000187:drug effects / Q000378:metabolism*; D014364:Tryptophan / Q000494:pharmacology*
chemical_list: D012701:Serotonin; D014364:Tryptophan; D006916:5-Hydroxytryptophan; D002997:Clomipramine; D011188:Potassium