AR and neurodegenerative disease: In line with an important role for AR signaling in regulating the permeability of the BBB is the observation that inhibition of ARs by caffeine (a broad-spectrum AR antagonist) prevents the alteration of BBB function induced by cholesterol or 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) in animal models of neurodegenerative diseases [60, 61].