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). The gene discussed is SLC6A3; the disease is Parkinson disease.