SLC6A3 and Parkinson disease: Most preclinical studies have been performed using 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and 6-hydroxydopamine (6-OHDA) in PD animal models, where toxins enter dopamine neurons via dopamine transporter (DAT) and acutely kill specifically the dopamine neurons (Lotharius et al., 1999).