SLC6A3 and Parkinson disease: In Parkinson’s disease, the temporal profile of nigrostriatal neurodegeneration has been most often described by a negative mono-exponential function by histological studies,47,48 studies using radiotracers targeting the dopaminergic system29,40,49-53 or by NM-MRI.27,30 Some studies however have reported a linear decrease in dopamine function with advancing disease duration using DAT-SPECT54-56 or NM-MRI.31