We also used normal and 6-OHDA induced PD model rats to assess the effects of zosuquidar·3HCl (a specific P-gp inhibitor) mediated P-gp inhibition on free FLZ concentrations in the brain ECF and blood over time. In vivo microdialysis is a useful tool for evaluating drug passage across the BBB, particularly when used to study drug transporters in the CNS [20]. Here, PGP is linked to Parkinson disease.