Myocardial ischemic nociceptive signaling mediated by P2X3 receptor in rat stellate ganglion neurons.

Adenosine 5'-triphosphate (ATP) is implicated in peripheral pain signaling through activation of P2X receptors. P2X(3) receptors have a high level of expression in, and selective location on sensory afferents. P2X receptors, particularly the P2X(3) subtype, are identified as targets for novel analgesics. The stellate ganglion (SG) is peripheral sympathetic ganglia involved in heart function. Surgical interventions of sympathetic afferent pathways abolish or relieve angina pectoris, so it is showed that cardiac pain is mediated by the activation of afferents in sympathetic nerves. The cervicothoracic sympathetic ganglia, including the stellate ganglion, are implicated in sensations associated with myocardial ischemia or cardiac pain. In the present study we have examined P2X(3) involvement in cardiac nociceptive transmission. P2X receptor agonists activated currents (I(ATP)) in SG neurons. The I(ATP) amplitude and P2X(3) mRNA expression in myocardial ischemic injury group were much larger than those obtained in control group. Prostaglandin E(2) (PGE(2)) and substance P (SP) increased ATP-activated currents. P2X(3) receptor antagonist A-317491 reduced P2X agonist activated currents and P2X(3) mRNA expression. The results revealed that the myocardial ischemia induced the upregulation of P2X(3) receptor in function and morphous and P2X(3) receptor antagonist A-317491 inhibited P2X agonist activated currents and P2X(3) mRNA expression. The facts indicated that P2X(3) receptor in SG neurons was involved in cardiac nociceptive transmission.