Evaluation of 3H-paroxetine as a radioligand for in vivo study of 5-hydroxytryptamine uptake sites in mouse brain.

The distribution of radioactivity in the mouse brain after intravenous administration of 3H-paroxetine was in the order (highest to lowest) hypothalamus greater than cerebral cortex greater than cerebellum. The radioactivity in the hypothalamus and cerebral cortex after injection of 3H-paroxetine was significantly decreased by treatment with 6-nitroquipazine or paroxetine. HPLC and TLC analyses show that no radioactive metabolites were found in the mouse brain 3 h after intravenous administration of 3H-paroxetine. The present results indicate that 3H-paroxetine would be a suitable radioligand for in vivo study of 5-HT uptake sites in mouse brain.