P2X(7) receptors: properties and relevance to CNS function.

Among seven members of P2X ionotropic receptors activated by extracellular ATP, the P2X(7) subtype is unique in that it can function as a cation channel, a nonselective pore, or even a signaling complex coupled with multiple downstream components. Several roles of P2X(7) receptors have been described in CNS cells in the past decade, including release of cytokines and transmitters, modulation of presynaptic transmitter release, and activation of multiple signaling pathways. The finding that P2X(7) pores may directly mediate efflux of cytosolic glutamate, GABA, and ATP in glial cells is particularly interesting, as it provides a novel mechanism of glial transmitter release that may play important roles not only in physiological intercellular communication but also in pathological neural injury.