PET imaging of the brains of MPTP-treated cynomolgus or rhesus monkeys showed that the binding of DA transporter (DAT) ligand and the utilization of L-3,4-dihydroxyphenylalanine (L-dopa) progressively decreased in the striatum upon MPTP administration and the manifestation of parkinsonism [29], [30], [31]. This evidence concerns the gene SLC6A3 and Parkinsonism.