EFFECTS OF SPINAL CYCLOOXYGENASE-1(COX-1) ON MECHANICAL ALLODYNIA INDUCED BY POSTOPERATIVE PAIN IN RAT / 神经解剖学杂志

ABSTRACT

To identify the role of spinal cyclooxygenase (COX)-1 in the development and maintenance of postoperative pain, we examined the changes of COX-1 protein expression in lumbar spinal cord by immunohistochemistry and Western blot technique in rat plantar incision model at different time points (pre-incision or 2 h, 4 h, 6 h,12 h, 1 d, 2 d, 3 d, 5 d and 7 d after incision). We also studied the anti-allodynic effects of the COX inhibitors by intrathecal administration of non-selective COX inhibitors (ketorolac), selective COX-1 (SC-560) or COX-2 inhibitor (NS-398) immediately or 2 h, 24 h after incision. The mechanical allodynia was evaluated by using paw withdrawal threshold (PWT) response to mechanical stimulation on pre-incision, 2 h, 1 d, 2 d, 3 d, 5 d and 7 d after incision or 30 min after drug treatment. The result showed that COX-1 immunoreactive cells mainly focused in the superficial laminae of lumbar spinal dorsal horn and expression of spinal COX-1 protein increased after incision, peaked at 4 h (P＜0.01) and lasted for 12 h. Postoperative treatment with both SC-560 and ketorolac significantly alleviating the mechanical allodynia induced by skin incision, but NS-398 had no such effect. This study demonstrates that spinal COX-1 involves in the development and maintenance of postoperative hypersensitivity and intrathecal COX-1 inhibitor has anti-allodynic effect on incision pain in the rat.