Effects Of Cyclin Dependent Kinase 5 Inhibitor Roscovitine On Remifentanil-induced Hyperalgesia And The Expression Of NR2B And MGluR5 Phosphorylation In Spinal Cord

Objective:To investigate the effects of cyclin dependent kinase 5 inhibitor Roscovitine on remifentanil-induced hyperalgesia and the expression of NR2B and mGluR5 phosphorylation in spinal cord in rats.Methods:Sixty-three SD rats were randomly divided into 7 groups(n=9 each):control group(C);incisional pain group(I);Roscovitine group(ROS);remifentanil group(R);Roscovitine 25?g + remifentanil group(ROS 1+R);Roscovitine 50?g +remifentanil group(ROS 2+R);Roscovitine 100?g + remifentanil group(ROS 3+R).All rats were anesthetized with sevoflurane.A right hind paw plantar incision was performed in group I,ROS,R,ROS 1+R,ROS 2+R,ROS 3+R.Roscovitine(50?g/10t?l),(25?/10?l),(50?g/10?l),(10?g/10?l)was injected intrathecally 30 min before plantar incision in group ROS and ROS 1+R,ROS 2+R,ROS 3+R respectively,In group R and ROS 1+R,ROS 2+R,ROS 3+R,remifentanil(0.04 mg/kg,0.4 ml)was infused subcutaneously with a pump for 30 min at the moment of surgical incision.To evaluate the behavioral changes,paw withdrawal mechanical threshold(PWMT)and paw withdrawal thermal latency(PWTL)were measured at 24 h before incision and at 2 h,6 h,24 h,and 48 h after incision.The specimens were collected under deep anesthesia just after behavioral testings at 48 h:the right dorsal horn of the spinal cord L4.5 segments were removed rapidly,and the Western blot studies were performed to quantificate the expression of NR2B and mGluR5 phosphorylation in the spinal cord,what's more,the In vitro kinase assay was used to measure Cdk5 kinase activity in the spinal cord.Results 1)pain behavioral changes:before operation,no significant difference between groups in the PWMT and PWTL was found.Compared with the baseline,the treatment in group C did not produce significant changes of PWMT and PWTL(p>0.05).However,significant decreases of the PWTL(except group ROS)and PWMT were observed in other groups during the whole postoperative period.The PWTL in group ROS was considerably higher than group I(p<0.05),however,the phenomenon was not observed in PWMT.Compared with group I,the significant decrease of PWMT(6.410.6g vs 9.6±0.8g)and PWTL(14.4±1.7s vs 18.0±0.4s)(p<0.01)were observed at 2 h after incision in group R,and this level continued until 48 h after incision;The PWTL of ROS 1+R,ROS 2+R,ROS 3+R were all higher than group R,but only the PWMT of ROS 2+R,ROS 3+R were higher than group R(p<0.05).2)Western blot analysis:When compared with group C,intraoperative remifentanil infusion could increase the expression of Cdk5 and its activator p35/p25,then Cdk5 activity and the expression of NR2B,mGluR5 in spinal cord(p<0.01);the increases were significantly reduced by pretreatment of Cdk5-specific inhibitor Roscovitine(p<0.01).Conclusion:The rat model of incisional pain has been associated with an increase of NR2B tyrosine phosphorylation and mGluR5 phosphorylation in spinal cord.The activation of Cdk5,NR2B tyrosine phosphorylation and mGluR5 phosphorylation in spinal cord play a role in the postoperative hyperalgesia induced by remifentanil in a rat model of incisional pain.The pretreatment with Roscovitine,via inhibiting Cdk5 activity,NR2B tyrosine phosphorylation and mGluR5 phosphorylation in superficial spinal cord of rats,attenuated postoperative hyperalgesia induced by remifentanil.