Abstract: Abstract： Objective To investigate the influence of dexmedetomidine on expressions of protein kinase c (PKC)γ, calcium/calmodulin-dependent protein kinase (CaMK)Ⅱα and pCaMKⅡα in spinal cord in rats with incisional pain (IP) and remifentanil-induced hyperalgesia. Methods Forty male Sprague-Dawley rats, aged 2-3 months, weighing 240-260 g,were randomly divided into 5 groups (n=8 each): blank control group (group C), remifentanil+incisional pain group (group R+I), dexmedetomidine + remifentanil + incisional pain group (group D+R+I), dexmedetomidine + remifentanil + incisional pain + phorbol myristate acetate + DMSO group (group D+R+I+P+DMSO) and dexmedetomidine + remifentanil + incisional pain + DMSO group (group D+R+I+ DMSO). The incisional pain rat model was established by a plantar incision in left hind paw. Remifentanil was infused at a rate of 1.2 μg·kg-1·min-1 for 90 min via the caudal vein. Dexmedetomidine was adminis⁃ tered subcutaneously at a dose of 50 μg/kg at 30 min before plantar incision. Phorbol myristate acetate and DMSO were intrathecally injected at a dose of 10 μL. Paw withdrawal latency (PWL) to thermal stimulation and paw withdrawal threshold (PWT) to von Frey hair stimulation were measured 24 h before remifentanil infusion (T0) and at 2, 6, 24 and 48 h (T1-4) after intraveonus remifentanil injection. The rats were sacrificed after the last behavioral test and the L4- 6 segment of spinal cord was removed to determine the expressions of PKCγ, CaMKⅡα and pCaMKⅡα in spinal cord by Western blot analysis. Re⁃sults Compared with group C, the value of PWL was significantly shortened and PWT was significantly decreased except T0, and the expressions of PKCγ, CaMKⅡα and pCaMKⅡα were up-regulated in other groups. Compared with group R+I,the value of PWL was significantly prolonged and PWT was significantly increased, the expressions of PKCγ, CaMKⅡα and pCaMKⅡα were down-regulated in group D+R+I and group D+R+I+DMSO. Compared with group D+R+I, the value of PWL was significantly shortened and PWT was significantly decreased, the expressions of PKCγ, CaMKⅡα and pCaMKⅡα were up-regulated in group D+R+I+P+DMSO. Compared with group D+R+I+P+DMSO, the value of PWL was significantly prolonged and PWT was significantly increased, the expressions of PKCγ, CaMKⅡα and pCaMKⅡα were down-regulated in group D+R+I+DMSO. Conclusion Dexmedetomidine can reduce the expressions of PKCγ, CaMKⅡα and pCaMKⅡα in spinal cord in rats with IP and hyperalgesia induced by remifentanil.

Key words: hyperalgesia, spinal cord, protein kinase C, calcium-calmodulin-dependent protein kinase type 2, phorbol esters, rats, Sprague-Dawley, Dexmedetomidine, Remifentanil