ATP- and Adenosine-Mediated Signaling in the Central Nervous System: The Role of Extracellular ATP in Hippocampal Long-Term Potentiation

Abstract

Application of 10 μM ATP for 10 min transiently depressed, then slowly augmented, synaptic transmission in CA1 neurons, leading to long-term potentiation (LTP) (ATP-induced LTP). This ATP-induced LTP was blocked by addition of an N-methyl-D-aspartate (NMDA) glutamate receptor antagonist, D,L-2-amino-5-phosphonovalerate (5 μM). For ATP-induced LTP, delivery of test synaptic inputs once every 20 s to CA1 neurons could be substituted by application of 100 nM NMDA during ATP perfusion. In addition, ATP-induced LTP was blocked by co-application of an ecto-protein kinase inhibitor, K-252b (40 nM), whereas a P2X purinoceptor antagonist, pyridoxal-phosphate-6-azophenyl-2′,4′-disulphonic acid 4-sodium (50 μM), or a P2Y purinoceptor antagonist, basilen blue (10 μM), had no effect. These results, therefore, indicate that the mechanisms of ATP-induced LTP involve the modulation of NMDA receptors / Ca2+ channels and the phosphorylation of extracellular domains of synaptic membrane proteins, one of which could be the NMDA receptor / Ca2+ channel. Keywords:: long-term depression, NMDA receptor, extracellular phosphorylation, synaptic plasticity