Future Directions in P2 Receptor Research

Abstract

The identification and characterization of receptors for extracellular nucleotides has benefited substantially from modern molecular biological techniques, as this volume has attempted to chronicle. The rapid advancement provided by these molecular approaches has also highlighted perhaps the most important challenge facing researchers in the area—the identification of the cloned P2 receptor subtype(s) involved in each of the wide array of physiological and pathological processes affected by extracellular nucleotides. Information in the preceding chapters inspires confidence that this essential task will be facilitated in the near future by the availability of additional P2 receptor subtype-selective ligands, hopefully both agonists and antagonists. Although the number of cloned P2 receptors is already impressive, evidence indicates the existence of additional subtypes and it seems reasonable to expect a few surprises as the full range of signaling molecules for extracellular nucleotides becomes known. It is essential to establish whether or not other nucleotides, in addition to adenosine triphosphate (ATP) and adenosine diphosphate (ADP), function as endogenous extracellular signaling molecules through P2 receptors. If uridine triphosphate (UTP) or other nucleotides are shown to serve such a role, a re-evaluation of the current nucleotide receptor classification scheme may be required.