4-Bromo-6-nitroquipazine: a new ligand for studying 5-hydroxytryptamine uptake sites in vivo

The present study was undertaken to evaluate 2 bromo-derivatives (4-bromo-6-nitroquipazine and 6-bromoquipazine) of quipazine as potential ligands for studying 5-hydroxytryptamine (5-HT; serotonin) uptake sites in the brain in vivo. The inhibition experiments of [3H]5-HT uptake into synaptosomes from rat brain and of the binding of [3H]6-nitroquipazine to membranes of rat brain showed that 4-bromo-6-nitroquipazine and 6-bromoquipazine were very potent and selective inhibitors of 5-HT uptake in vitro, very close to that of 6-nitroquipazine. Furthermore, 4-bromo-6-nitroquipazine was about a 2-fold more potent inhibitor of specific binding of [3H]6-nitroquipazine in vivo in the hypothalamus of mouse brain than 6-bromoquipazine. Thus, 4-bromo-6-nitroquipazine seems to be superior to 6-bromoquipazine, as a potential ligand for in vivo imaging of 5-HT uptake sites in the brain.