AIMTo explore the effects of intrathecal injection of selective cyclooxygenase-1 (COX-1) inhibitor, SC-560, on mechanical allo dynia and spinal ERK protein expression in rats with postoperative pain.

METHODSRats were divided into 4 groups: control group, postoperative pain group, SC-560 group and DMSO group. Mechanical withdrawal threshold (MWT), immunohistochemical and Western blotting technique were used to evaluate mechanical hypersensitivity and the expression of phospho-ERK in the spinal cord, respectively.

RESULTS(1) Behavior test rats developed allodynia 1 h after operation and SC-560 100 microg administrated intrathecally demonstrated a significant reduction in postoperative hypersensitivity. (2) Immunohistochemical staining Phospho-ERK positive neurons in the rat superficial spinal dorsal horn increased significantly 1 h after incision compared with that of non-incision group. Intrathecal administration of SC-560 preoperatively could significantly reduce the number of phospho-ERK positive neurons. (3) Western blot expression of phospho-ERK1/2 protein in the lumbar spinal cord increased significantly 1 h after incision and decreased by intrathecal injection of SC-560.

CONCLUSIONSC-560 administrated intrathecally can inhibit mechanical hypersensitivity induced by postoperative pain in rats and this anti-allodynic process may mediated by spinal ERK.