Purinoceptor nomenclature: A status report

<jats:title>Abstract</jats:title><jats:p>In the field of purinoceptors, the P<jats:sub>1</jats:sub>‐adenosine and P<jats:sub>2</jats:sub>‐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/P<jats:sub>1</jats:sub> receptor class, the generally accepted nomenclature has been that of A<jats:sub>1</jats:sub> and A<jats:sub>2</jats:sub>, while P<jats:sub>2</jats:sub> receptor have been defined as P<jats:sub>2x</jats:sub>, P<jats:sub>2y</jats:sub>, and so on. The incorporation of newer receptors, characterised either by the actions of available compounds on defined tissues 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 A<jats:sub>1</jats:sub>, A<jats:sub>2a</jats:sub>, and A<jats:sub>2b</jats:sub> receptors, be further described by numerical subscript, i.e., A<jats:sub>3</jats:sub>, A<jats:sub>4</jats:sub>, until such time as pharmacological and molecular biological data provided evidence for their relationship, if any, to the A<jats:sub>1</jats:sub>/A<jats:sub>2</jats:sub>, classes. For ATP and other purine nucleotide receptors, subtypes of which were designated by letters rather than numbers, the P<jats:sub>2X</jats:sub> and P<jats:sub>2Y</jats:sub>, receptors proposed by Burnstock major families of P<jats:sub>2</jats:sub> 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 of the IUPHAR nomenclature initiative. © 1993 Wiley‐Liss, Inc.</jats:p>