A full platelet aggregation in response to ADP occurs by the stimulation of P2Y1 receptor, followed by P2Y12 activation (Figure 1). P2Y1 is a Gq-coupled receptor that initiates ADP-induced platelet aggregation through the stimulation of phospholipase C and phosphatidylinositol-signaling pathway. P2Y12R is a seven transmembrane domain receptor. It mediates the inhibition of adenylate cyclase and, in turn, cyclic AMP (cAMP) production via the coupling to Gαi leading to impaired protein kinase A (PKA) activation and a subsequent inhibition of vasodilator-stimulated phosphoprotein (VASP), which restrains either secretory or adhesive events in platelets (Figure 1).