Decreased MnSOD expression was also observed in PD-causing neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-treated animal models, with severe loss of abnormal dopamine transporter (DAT)-immunoreactive DA neurons in the striatum and the substantia nigra [161,162]. This evidence concerns the gene SLC6A3 and Parkinson disease.