The Role Of Nav1.8 In Rat Doral Root Ganglia When Remifentanil Induced Hyperalgesia

Objective: To observer the expression of Navl.8 in the dorsal root ganglion,when hyperalgesia was induced by remifentanil and remifentanil-incision pain in rats model,the role of Nav1.8 in the dorsal root ganglia on remifentanil and remifentanil-incision pain induced hyperalgesia also was researched.Methods:Forty eight adult male Sprague-Dawley rats were randomly divided into 6groups.Control group(C grooup);Remifentanil group(R group);Remifentanil+A803467 group(R+Agroup);Remifentanil+incisional group(R+Igroup);renifentanil+incisional+A803467group(R+I+Agroup);remifent anil+incisional+vopivacaine group(R+I+L);each consisting of eight rats.Two catheter for the drug infusion were implanted into the jugular vein and lumber L3-4clearance for all rats.On the third day after implanted catheters.Control group(C group),Normal saline 1.0 ml·kg-1·min-1 ,and it was continued for 2 h. R group was injected with remifentaini by the jugular vein ,and it was continued for 2 h,the RA group was injected with A-803467 20 mg/kg ,10min later then it was injected with remifentanil by the jugular vein, and it was continued for 2 h ;the RI group was injected with remifentanil by the jugular vein,and rats underwented two hind paws surgery at the same time;the RIAgroup was injected with A-803467 20 mg/kg ,10min later it was injected cotinuously remifentanil by the jugular vein, and it was continued for 2 h,and rats underwented two hind paws surgery at the same time .RIL group was injected with ropivacaine 0.12 ml/kg, 10min later it was injected with remifentanil by the jugular vein for 2h,and rats underwented two hind paws at the same time.The threshold of thermal pains were evaluated by the radiant heat tail-flick test before venipuncture(T0), before administration (T1),after administration 1/2 h?1 h?2 h and after drug withdrawal 1/2 h(respectively T0?T5) .using RT -PCR and immunohistochemical to examined the expression of Nav1.8 in the dorsal root ganglia.Results: The body weight and the thermal pain threshold of based value(T0) and former drug (Ti) were no significant for each group rats. In T2?T3?T4 point , the thermal pain threshold of R group?RA group?RI group?RIA group and RIL group were significant increased compared to C group(P<0.05).In T5 point, after drug withdrawal, the thermal pain threshold of R group?RA group?RI group and RIAgroup were significantly decreased compared to C group(P<0.05) ; There were no significant difference of the thermal pain threshold between RIL group and C group(P>0.05); the thermal pain threshold of R group was significantly decreased compared to RA grooup(P<0.05); the thermal pain threshold of RI group was significant decreased compared to R group?RIAgroup and RILgroup (P<0.05) ; and the thermal pain threshold of RIAgroup was significant deceased comppared to RIL group(P<0.05).The result of RT-PCR and immunohistochemistry : the expression of the Nav1.8 mRNA and protein of R group and RI group were significant increased compared to C group(P<0.05);the expression of the Nav1.8mRNA and protein of RA group?RIA group and RIL group were significant decreased compared to C group(P<0.05). And then, the expression of the Nav1.8 mRNA and protein of R group?RIA group and RILgroup were significant decreased compared to RI group(P<0.05);Conclusion: The expression of the channel Nav1.8 increased in the rat dorall root ganglia when Remifentanil and Remifentanil-incision pain induced hyperalsia in rats; the channel Na.v1.8 in rat doral root ganglia was not the only one channel invollved in Remifentanyl and Remifentanyl - incision pain induced hyperalgesia; Ropivavaine can effctively reduce the expression of N av1.8 to block hyperalgesia induced by remifentanil and remifentanil-incisional pain in rats.