Electroacupuncture suppresses spinal expression of neurokinin-1 receptors induced by persistent inflammation in rats.

It has been demonstrated that electroacupuncture (EA) significantly suppresses behavioral hyperalgesia in a rat model of persistent inflammatory pain and that neurokinin-1 (NK-1)/substance P (SP) receptors play important roles in nociception and hyperalgesia at the spinal cord level. The present study investigated spinal NK-1 receptor involvement in EA-produced suppression of hyperalgesia in a rat model of persistent inflammatory pain. The results showed that hind paw inflammation induced a significant increase of NK-1 receptor expression in the spinal dorsal horn and that this effect was significantly suppressed by EA. This suggests that EA-induced suppression of hyperalgesia is involved, at least partly, in the suppression of the spinal NK-1 receptors induced by sustained peripheral nociceptive input.