Platelet receptors for ADP plays a key role in the formation of the clot and vascular pathogenesis. P2Y receptors act via two G-proteins, which pulls behind activation of intracellular second messengers. P2Y1 initiates aggregation through mobilization of calcium, while the recently identified receptor P2Y12 inhibiting adenylate cyclase is necessary for the full response. In contrast, the P2X1 ion channel high-speed transmission, which participate in platelet activation is still not fully understood. ADP platelet receptors are potential targets for antiplatelet drugs such as ticlopidine and clopidogrel, and knowledge of their mechanism of action helps explain the role in the prevention of cardiovascular pathologies.