Inhibitory Effect Of A1 Adenosine Receptor Activation On ATP Current In Primary Sensory Neurons And Its Intracellular Mechanis

Objective:Pain widely exists in the occurrence and development of various diseases and disturbed people’s life and mental state for a long time.Purinergic signaling is involved in multiple pain processes.P2X3 receptor is a key target in pain therapeutics,while A1 adenosine receptor signaling plays a role in analgesia,and both of them are expressed in DRG cells.However,it remains unclear whether there is a link between them in pain.We therefore investigated the effect of A1 adenosine receptor on the functional activity of P2X3 receptor by electrophysiological and behavioral experiments.Methods:Using the Electrophysiological patch-clamp technique to record the electrophysiological activity mediated by P2X3 receptor in DRG cells isolated from rats.We also observed the effective of CPA inα,β-me ATP-induced nociceptive behaviors in rats.Intraplantar injection of CPA andα,β-me ATP to observed the effect of CPA on mechanical hyperalgesia in rats.Results:A1 adenosine receptor agonist N~6-cyclopentyladenosine(CPA)concentration dependently suppressed P2X3 receptor–mediated andα,β-methylene-ATP(α,β-me ATP)–evoked inward currents in rat dorsal root ganglion(DRG)neurons.CPA significantly decreased the maximal current response toα,β-me ATP,as shown a downward shift of the concentration–response curve forα,β-me ATP.CPA suppressed ATP currents in a voltage-independent manner.Inhibition of ATP currents by CPA was completely prevented by the A1 adenosine receptor antagonist KW-3902,and disappeared after the intracellular dialysis of either the Gi/o protein inhibitor Pertussis Toxin,the Adenylate Cyclase activator Forskolin,or the c AMP analog 8-Br-c AMP.Moreover,CPA suppressed the membrane potential depolarization and action potential bursts,which were induced byα,β-me ATP in DRG neurons.Finally,CPA relievedα,β-me ATP-induced nociceptive behaviors in rats by activating peripheral A1 adenosine receptors.Conclusions:These results indicated that CPA inhibited the activity of P2X3receptors in rat primary sensory neurons by activating A1 adenosine receptors and its downstream c AMP signaling pathway,revealing a novel peripheral mechanism underlying its analgesic effect.