DRD2 and Parkinson disease: A clinical study used SPECT to assess the dopamine D2 receptor and dopamine transporter (DAT) in PD patients pre-surgery and at 12 months post-surgery; the unified PD rating scale (UPDRS) scores post-surgery remarkably improved in those patients and titrated down their medication, but no changes in DAT availability or an increase in D2 receptor binding were detected (Hesse et al., 2008).