Towards a revised nomenclature for P1 and P2 receptors.

The classification of receptors for adenosine, ATP and ADP (collectively called purinoceptors) has seen a number of developments in the past three years. The important division of receptors into two major classes1 (1) adenosine (P1) receptors and (2) P2 purinoceptors, first suggested by Burnstock in 1978 (Ref.2), has been an abiding one that has set the stage for further subdivision of P2 purinoceptors into P2X and P2Y subtypes on the basis of pharmacological properties3. Later, Dubyak4 summarized the evidence that ATP worked through two different transduction mechanisms: intrinsic ion channels and G protein-coupled receptors. This information, coupled with the cloning of purinoceptors in 1993/94, led Abbracchio and Burnstock5 to propose that purinoceptors should be classified in two families: G protein-coupled receptors termed P2Y purinoceptors, and intrinsic ion channels termed P2X purinoceptors. Developments in recent years have borne out these expectations and a revised nomenclature, essentially adopting the Abbracchio and Burnstock proposal, can now be proposed.