6-FLUORO-SEROTONIN AS A SUBSTRATE FOR THE NEURONAL SEROTONIN TRANSPORTER

6-Fluoro-serotonin (6F-5-HT) was previously identified in the rat brai n after peripheral administration of 6-fluoro-DL-tryptophan, a seroton in (5-HT) synthesis inhibitor. These present studies, performed with r at brain synaptosomes show that: i- neuronal 6F-5-HT uptake partly inv olved the 5-HT transporter since it was inhibited by clomipramine, a 5 -HT uptake inhibitor, ii-6F-5-HT blocked the synaptosomal uptake of H- 3-5-HT, with an IC50 value of 98 +/- 13 nM, and iii- 6F-5-HT induced H -3-5-HT release from preloaded synaptosomes, with an EC(50) value of 9 5 +/- 6 nM; this release was decreased in the presence of clomipramine , suggesting the involvement of the 5-HT transporter. This release was also reduced when using synaptosomes from reserpinized rats, suggesti ng that the vesicular pool also participates to the H-3-5-HT release i nduced by 6F-5-HT. So, 6F-5-HT behaved as a substrate for the 5-HT neu ronal transporter.