PURINOCEPTOR NOMENCLATURE - A STATUS-REPORT

In the field of purinoceptors, the P1-adenosine and P2-ATP system proposed by Burnstock some 15 years ago has provided a cornerstone for receptor nomenclature [Burnstock and Kennedy, 1985: Gen Pharmacol 16:433-440.] For the adenosine/P1 receptor class, the generally accepted nomenclature has been that of A1 and A2, while P2 receptors have been defined as P(2x), P(2y), and so on. The incorporation of newer receptors, characterised either by the actions of available compounds on defined tissue systems or by the cloning and expression of purinoceptors, into this framework provides the challenge of melding the 'old' with the 'new.' An open meeting of the IUPHAR Purine Receptor Nomenclature Subcommittee held at the Purine Club's 'Purine '92' in Milan in June of 1992 focused on this issue with input from world leaders in the area of purine research. It was recommended from this meeting that adenosine receptors, in addition to the classical A1, A(2a), and A(2b) receptors, be further described by numerical subscripts, i.e., A3, A4, until such time as pharmacological and molecular biological data provided evidence for their relationship, if any, to the A1/A2 classes. For ATP and other purine nucleotide receptors, subtypes of which were designated by letters rather than numbers, the P(2x) and P(2y) receptors proposed by Burnstock and Kennedy were accepted on the basis of historical precedent and usage, representing the 2 major families of P2 receptors utilizing ligand-gated cation channels and G-proteins, respectively. Some concerns were expressed in regard to the apparent random walk through the alphabet in terms in the naming of P(2n), P(2t), P(2u), and P(2z) receptors, which are inconsistent with the ground rules of the IUPHAR nomenclature initiative.