SLC6A3 and Parkinson disease: Accordingly, PD patients, who displayed a significant decrease of DAT binding after long-term treatment with L-DOPA had a mean Unified Parkinson’s Disease Rating Scale (UPDRS) score of 23.9 ± 6.0 (Guttman et al., 2001), whereas in studies, in which no alterations of DAT binding were observed, mean UPDRS scores were 17–47% higher (Schillaci et al., 2005: UPDRS, 35.1 ± 11.8; Nurmi et al., 2000: UPDRS, 31.0 ± 48.0; Parkinson Study Group, 2002: UPDRS, 30.6 ± 11.4; Parkinson Study Group, 2004: UPDRS, 28.0 ± 13.0).