International union of pharmacology. XXIV. Current status of the nomenclature and properties of P2X receptors and their subunits

ATP acts as a humoral mediator to control cell function extracellularly. Th e receptors that mediate the actions of ATP belong to two classes, the meta botropic P2Y receptors and the transmitter-gated, ion channel P2X receptors . This review describes the structure, distribution, function, and ligand r ecognition characteristics of P2X receptors, which comprise seven distinct subunits that can function as both homo- and hetero-polymers. The pharmacol ogy of P2X receptors is complicated by marked differences between species o rthologues. The current nomenclature is based largely on recombinant recept or studies and detailed knowledge of endogenous P2X receptors in native tis sues is limited because of lack of good selective agonists and antagonists for each receptor type.