Under these pathological circumstances of α-synuclein aggregation, there was an approximately 90% reduction in VDR, and an 80% reduction in P-gp endothelial expression in the ventral midbrains of combinatorial PD mouse models compared to that in the ventral midbrains of control mice (Figure S2B,C, and Figure 3D,E). Here, VDR is linked to Parkinson disease.