Enhancement Of ET-1 On P2X3 Receptor Electrophysiological Activity In Primary Sensory Neurons

Objective:Endothelin-1(ET-1),an endogenous vasoconstrictor,has been known as a pro-nociceptive agent involved in multitude of pain.ET-1 acts on endothelin receptors on vascular endothelial cells,sensitizes release of ATP,which then acts on P2X3receptors on nociceptors and results in mechanical hyperalgesia.Both endothelin receptors and P2X3 receptors are present in primary sensory neuron,where it remains unclear whether there is an interaction between them.Herein,we reported that ET-1potentiated the electrophysiological activity of P2X3 receptors in rat dorsal root ganglia(DRG)neurons.Methods:The electrophysiological activity of P2X3 receptors was recorded by whole cell patch clamp technique in DRG neurons isolated from rats.Mechanical hyperalgesia was induced by intraplantar injection of ET-1 and/orα,β-methylene-ATP(α,β-meATP)in rats.We observed that whether P2X3 receptor blockers A-317491relieve ET-1 induced mechanical hyperalgesia.Results:ET-1 concentration-dependently increasedα,β-meATP-evoked inward currents,which were mediated by P2X3 receptors.ET-1 shifted theα,β-meATP concentration-response curve upwards,with an increase of 34.38±4.72%in the maximal current response toα,β-meATP in the presence of ET-1.ET-1 potentiation ofα,β-meATP-evoked currents was voltage-independent.ET-1 potentiated P2X3receptor-mediated currents through endothelin-A receptors(ET_AR),but not endothelin-B receptors(ET_BR).ET-1 potentiation was inhibited by blockade of intracellular G-protein or protein kinase C(PKC)signaling.Moreover,there is a synergistic effect on mechanical allodynia induced by intraplantar injection of ET-1andα,β-meATP in rats.Pharmacological blockade of P2X3 receptors also alleviated ET-1-induced mechanical allodynia.Conclusions:These results suggested that ET-1 sensitized P2X3 receptors in primary sensory neurons via an ET_AR and PKC signaling pathway.Our data provide evidence that cutaneous ET-1 induced mechanical allodynia not only by increasing the release of ATP from vascular endothelial cells,but also by sensitizing P2X3 receptors on nociceptive DRG neurons.