Purinoceptors: Ontogeny and phylogeny

The majority of studies of the functional distribution of purinoceptors have been carried out with mammalian preparations. The objective of this article is to review the disparate literature describing purinoceptor-mediated effects in invertebrates and lower vertebrates and, in view of the concept that ontogeny repeats phylogeny, to review also the evidence for purinoceptor involvement in the complex signaling involved in embryonic development. Even with the limited information currently available, it is clear that purinoceptors are involved in early signalling in vertebrate embryos; one novel G protein-coupled P2Y receptor has already been cloned and characterized in frog embryo and hopefully more will follow. It is also clear that purinoceptors for both adenosine and ATP are present in early evolution and play a number of different roles in most, if not all, invertebrate and lower species. However, until selective agonists and antagonists are identified for the recently cloned purinoceptors subtypes in vertebrates, it will not be possible to resolve questions concerned with the evolution of these subtypes. Molecular cloning of genes encoding receptors for purines and pyrimidines from invertebrates and lower vertebrates represents an alternative approach to advancing knowledge in the area. (C) 1997 Wiley-Liss, Inc.