Effects of selective tumor necrosis factor-alpha inhibition to pain-behavioral changes caused by nucleus pulposus-induced damage to the spinal nerve in rats

Application of nucleus pulposus to the spinal nerve and displacement of the adjacent nerve results in behavioral changes in rats. It has been reported that treatment with the tumor necrosis factor-alpha (TNFα) inhibitor, infliximab, significantly reduces spontaneous pain behavior in this animal model. However, there have been no reports of the effects of infliximab on mechanical or thermal hyperalgesia using this model. Disk incision and adjacent spinal nerve displacement were performed with (n = 6) or without (n = 6) injection of infliximab. A control group also underwent sham surgery (n = 6). The animals were tested for 3 days before and on days 1, 3, 7, 14, and 21 after surgery. Non-noxious mechanical thresholds were tested by determining the hind paw withdrawal response to von Frey hair stimulation of the plantar surface of the footpad with a touch stimulator. Thermal nociceptive thresholds were tested using a sensitive thermal testing device. While disk incision with displacement surgery rats showed mechanical and thermal hyperalgesia after surgery on the experimental side, neither rats treated with infliximab nor the sham operation controls showed these effects. Injection of infliximab seemed to prevent mechanical and thermal hyperalgesia caused by the combination of disk incision and nerve displacement.