The human P2Y12 is an ADP receptor involved in platelet aggregation. ADP initiates platelet aggregation by simultaneous activation of two G protein-coupled receptors, P2Y1 and P2Y12. Activation of P2Y1 stimulates phospholipase C and triggers shape change, while P2Y12 coupled to Gi also involved in modulating thrombosis and hemostasis and therefore is a good drug target for antithrombotic drugs. P2Y receptors are expressed in a variety of tissues including platelets, endothelia, smooth muscle, CNS, osteoblasts , beta-islet cells as well as in commonly used CHO-K1 and HEK293 cells. We therefore chose to express the P2Y12 receptor in 1321N1 astrocytoma cells, which have minimal endogenous receptor.