PGP and Parkinson disease: The focus of this study was to determine whether coadministration with Tet, a potent inhibitor of P-gp, could restore the neuroprotective effects of GSH on the nigrostriatal system in 6-hydroxydopamine- (6-OHDA-) lesioned rat models of PD, as well as in PD rats undergoing long-term L-dopa treatment.