PGP and Alzheimer disease: The existing reports are conflicting: it has been revealed that brain capillaries of Alzheimer's patients have reduced expression of P-gp [235] and increased expression of BCRP [234]; however, a recent study by confocal microscopy that quantified peak fluorescence values of cross-sectional profiles of brain microvessels, revealed expression of P-gp protein to be significantly lower in hippocampal vessels of patients with AD compared to normal individuals, whereas that of MRP4 or BCRP protein was not changed [236].