Diadenosine polyphosphate receptors from rat and guinea-pig brain to humannervous system

Diadenosine polyphosphates are a family of naturally occurring nucleotidic compounds present in secretory vesicles together with other chemical messen gers. The exocytotic release of these compounds permits them to stimulate r eceptors termed "purinoceptors" or "ATP receptors." Purinoceptors for nucle otides are named P2 in contrast with those sensitive to nucleosides (P1). P 2 receptors are fur ther subdivided into metabotropic P2Y receptors, furthe r divided into 5 subtypes, and ionotropic P2X receptors, with 7 different s ubtypes. Diadenosine polyphosphates can activate recombinant P2Y(1), P2Y(2) , and P2Y(4) and recombinant homomeric P2X(1), P2X(2), P2X(3), P2X(4), and P2X(6), Heteromeric P2X receptors change their sensitivity to diadenosine p olyphosphates when co-assembly between different subunits occurs. Diadenosi ne polyphosphates can activate specific receptors termed dinucleotide recep tors or P4 receptors, which are insensitive to other nucleosides or nucleot ides. The P4 receptor is a receptor-operated Ca2+ channel present in rat br ain synaptic terminals, stimulated by diadenosine pentaphosphate and diaden osine tetraphosphate. This receptor is strongly modulated by protein kinase s A and C and protein phosphatases. The dinucleotide receptor is present in different brain areas, such as midbrain (in rat and guinea-pig), cerebellu m (in guinea-pig), and cortex (in human). (C) 2000 Elsevier Science Inc. Al l rights reserved.