The most widely studied, and AD related ABC transporter at the BBB, Abcb1 or P-glycoprotein (P-gp) was also examined by QPCR in isolated brain microvessels and by immunohistochemistry in the frontal cortex and hippocampus of wild-type and APOB-100 transgenic mice. The gene discussed is ABCG2; the disease is Alzheimer disease.