THE NEUROTRANSMITTER ROLE OF DIADENOSINE POLYPHOSPHATES

Diadenosine polyphosphates present at the cytosol can be transported t o secretory granules allowing their exocytotic release, Extracellularl y, they can act through specific metabotropic or ionotropic receptors, or as analogues of P2X and P2Y nucleotide receptors, The specific ion otropic receptor P4 is present in synaptic terminals, and modulated by protein kinases (PK) A and C and protein phosphatases. Activation of PKA or PKC, directly or through membrane receptors, results in a decre ase of affinity or in reduction of the Ca2+ transient respectively. Ad enosine and ATP, both products of the extracellular destruction of dia denosine polyphosphates, acting through Al or P2Y receptors respective ly, are important physiological modulators at the P4 receptor. (C) 199 8 Federation of European Biochemical Societies.