SLC6A3 and Parkinson disease: Conversely, in a recent PET study using 11C-PE2I (a radioligand with high striatal binding and greater DAT specificity than the others), the authors found not only a high correlation between the reduction in striatal DAT density and PD symptom severity at baseline, but even a significant negative correlation between change in motor severity (both UPDRS-III and bradykinesia/rigidity subscores) and DAT binding in the caudate and posterior putamen [184,230].