Experiments indicate that P2Y1,2,4,6 present on endothelial cells play an important role in preventing the vasoconstriction of brain vessels and lowering the CBF caused by Aβ-triggered release of NO, prostaglandins, and EDHF, and that process seems to be important at the initial stages of AD [6, 61]. The gene discussed is P2RY1; the disease is Alzheimer disease.