ABCB1 and Parkinson disease: For example, Bartelset al. found increased brain uptake of [11C]verapamil inPD patients, suggesting decreased P-glycoprotein efflux activity.69 Furthermore, Al-Bachari et al. showed greatercontrast agent transfer across the BBB in PD patients compared tohealthy controls, reflecting increased BBB permeability.70 Overall, substantial evidence points to BBBimpairment as a critical pathophysiological component of PD.