Involvement Of 5-HT_2A Receptor-PKC-GlyT2 Pathway In The Hyperalgesia Of Rats With Incisional Pain

Objective To investigate whether 5-HT_2A receptor-PKC-Gly T2 pathway is involved in the hyperalgesia of rat incisional pain.Method Adult male SD rats were used to generate incisional pain model,assess the pain behavior and execute for western blot.To begin with,we investigate the effects of TCB-2,a selective agonist of 5-HT_2A receptor,on paw withdrawal threshold to mechanical stimulus?PMWT?of rats with incisional pain by intrathecal administration of TCB-2 in a dose gradient of 3?g,10?g,30?g,100?g,200?g and assessing PMWT before and after 1h,2h,3h,4h,5h and 6h of intrathecal administration.In addition,we observe whether ketanserin,a selective antagonist of 5-HT_2A receptor,could reverse the analgesia effect of TCB-2 by intrathecal administration of both ketanserin and TCB-2 and verify the analgesia effect of TCB-2 from another point of view.We also observe the effect of TCB-2 on paw withdrawal thermal latency?PWTL?.Finally,we investigate the effects of strychnine,an antagonist of glycine receptor?Gly R?and chelerythrine,inhibitor of PKC,on hyperalgesia of rats with incisional pain by intrathecal administration of both strychnine and TCB-2 or both chelerythrine and TCB-2 and assessing PMWT before and after 1h,2h,3h,4h,5h and 6h of intrathecal administration.In molecular biological part,we detect the expression of membrane glycine transporter 2?Gly T2?in spinal cord by western blot at the time point of 1,3,5 and 7 hour after incisional pain operation and verify the involvement of 5-HT_2A receptor-PKC-Gly T2 pathway on incisional pain from a molecular perspective.Result After investigating the effects of 5-HT_2A receptor intervention on pain behaviors,we found that the PMWT significantly increased at 1h after intrathecal administration of TCB-2 in all doses when compared with their sham group?P<0.05?and the analgesia effect of TCB-2 was dose-dependent.The duration of TCB-2 was 4h among three groups of 30?g,100?g,200?g,while 2h and 1h in group of 10?g and 3?g,respectively?P<0.05?.The selective antagonist of 5-HT_2A receptor ketanserin could reverse the analgesia of TCB-2 after intrathecal administration of both ketanserin and TCB-2?P<0.05?.In addition,we found that there was no significant change in PWTL in group TCB-2 100?g when compared with their sham group?P>0.05?.In western blot,significant increases in the protein levels of membrane Gly T2 were detected in the spinal cord after 1h of incisional pain operation of rats when compared with sham group?P<0.05?.In addition,we also found that strychnine and chelerychrine could both reverse the analgesia of TCB-2?P<0.05?.Conclusion These results show that 5-HT_2A receptor may be involved in the hyperalgesia of rats with incisional pain and 5-HT_2A receptor agonist TCB-2 induces a dose-dependent analgesic effect on acute incisional pain.The optimal dosage of TCB-2 was 100?g,which could last 4h of analgesia after single intrathecal administration.Besides,there is a relationship between hyperalgesia induced by incisional pain and upregulation of membrane Gly T2 in spinal cord.Finally,the analgesic effect of TCB-2 can be reversed by Gly R antagonist strychnine and PKC inhibitor chelerythrine.These data suggest that 5-HT_2A receptor-PKC-Gly T2 pathway may be involved in the hyperalgesia of rats with incisional pain,which may be a promising treatment target of acute pain.