The P2Y receptors belong to the G-protein coupled receptors superfamily.They mediate the actions of the extracellular nucleotides (ATP, ADP, UTP AND UDPA. Eight functional mammalian P2Y receptors have been described: P2Y1, P2Y2, P2Y4, P2Y6, P2Y11, P2Y12, P2Y13, and the UDP-glucose receptor, now renamed P2Y14.The P2Y12 receptor is co-expressed with P2Y1 receptor on platelets leading to shape change, aggregation, and rise in intracellular Ca2+ upon activation.The only other expression of P2Y12 was found in brain, according to results of reverse transcription-polymerase chain reaction and northern blotting.The P2Y12 receptor has become a target for potential therapeutic drugs for the treatment of thromboembolism and other clotting disorders