DRD2 and Parkinson disease: We found a significant increase in the expression of D2R in PD (P < 0.01, one-way ANOVA), but not PD-D (P > 0.05, one-way ANOVA), mice when compared to naïve controls (Figures 4E,F; PD mice, 123 ± 15%; PD-D mice, 112 ± 22%; % of naïve control mice ± SEM; n = 15).