Abstract: Objective To study the changes of connexin 32 (Cx32) and Cx43 signals in the dorsal horn of spinal cord of rat with neuropathic pain induced by spared nerve injury (SNI) to sciatic nerve, and the analgeaic effect of 10μl carbenoxolone (CBX, a gap junction blocker, 1mmol/L）on neuropathic pain via intrathecal administration. Methods Adult SD rats were randomly divided into 3 groups, normal group (the animals did not receive any treatment), sham group (incised the skin and only exposed the sciatic nerve) and the SNI group, exposed three branches of the sciatic nerve, i.e. the tibial nerve, the common peroneal nerve and the sural nerve, and cut the tibial nerve and the common peroneal nerve but remained sural nerve. The paw withdrawal mechanical threshold (PWMT) of normal, sham and SNI groups was measured at 1day before SNI and at 3, 5, 10, 20 and 30 days after SNI, then the animals were killed and the spinal cords (L4-S1 segments) were removed and were used for Western blotting and anti-Cx32 and anti-Cx43 immunofluorescent staining. CBX was intrathecally injected at 20 days after SNI, and measured PWMT induced with an innocuous mechanical von Frey filaments stimulation. Results The PWMT of left behind leg in normal and sham groups did not reduce, while the left behind leg in SNI animals developed a conspicuous hypersensitivity to innocuous mechanical von Frey filaments stimulation. The PWMT of SNI rat decreased significantly as compared with normal and sham groups, and peaked at 20 days after SNI, it could maintain for as long as the animals were monitored. AntiCx32 and antiCx43 immunofluorescent reaction in the dorsal horn of spinal cord of SNI side increased significantly as compared with that in normal and sham group or the nonSNI side. After intrathecal injection of CBX 3hours, the PWMT of SNI side increased from the(2.5±1.0)g to (20.0±3.2)g, CBX inhibited the mechanical allodynia. In NS intrathecal injection group did not affect PWMT on SNI rats. Conclusion The gap junction

Key words: Neuropathic pain, Spinal cord, Connexin, Immunohistochemistry, Rat 