Overview. Purinergic mechanisms.

An overview of the history of studies of the biological actions of extracellular ATP is presented. The basis of the subdivision of receptors for purines into P1-purinoceptors for adenosine and P2-purinoceptors for ATP and ADP are considered, as well as the recent proposal for subdivision of the ATP receptors into P2X-, P2Y-, P2Z-, and P2T- purinoceptor subtypes. These purinoceptor subtypes are discussed with respect to their transduction mechanisms, their distribution, and their physiological roles, including their roles in cotransmission and neuromodulation.