Ectopic purinergic sensitivity develops at sites of chronic nerve constriction injury in rat

The possibility that ectopic purinergic sensitivity develops following peripheral nerve injury was investigated in chronic constriction injury (CCI). Spontaneous firing of A-fibers originated from the injury site or from sensory endings of afferents in the contralateral sciatic nerve. ATP injected intravenously excited most of the injured fibers whereas none of the contralateral afferents responded to ATP. The ATP-induced effect was blocked by the P2 receptor antagonist reactive blue 2, but not the P1 receptor antagonist aminophylline. Neither the alpha-adrenoreceptor antagonist phentolamine nor the cyclooxygenase inhibitor indomethacin attenuated the ATP-evoked effect. We conclude that a novel ectopic purinergic sensitivity mediated by P2 receptors develops at sites of the CCI of nerves in the rat, which may contribute to neuropathic pain.