The P2Y receptors belong to the G-protein coupled receptors superfamily. P2Y receptors mediate the actions of the extracellular nucleotides (ATP, ADP, UTP and UDP) and regulate several physiologic responses, among them, cardiac function, platelet aggregation and SMC proliferation.The mammalian P2Y family currently includes eight functional receptors; P2Y1, P2Y2, P2Y4, P2Y6, P2Y11, P2Y12, P2Y13, and the UDP-glucose receptor, now renamed P2Y14.The P2Y4-receptor is highly expressed in the placenta and with lower levels at lung and vascular smooth muscle.The human P2Y4 receptor is highly selective to UTP while rat P2Y4 receptor is equally activated by both UTP and ATP and also by other triphosphate nucleotides such as Ap4A.Recently it has been shown that P2Y4 receptor is involved in differentiation and cell death of human neuroblastoma SH-SY5Y cells.