DRD2 and Parkinson disease: Western blot results showed that the D2R protein expression level in the PD group was significantly down-regulated compared with the Control group (p < 0.01); compared with the PD group, the expression level of D2R protein in the striatum in PD + Ex group was significantly up-regulated, but still significantly lower than that in the Control group (Figure 7, p < 0.05).