Effect Of Paeoniflorin On Spinal Microglia Proliferation And Activation For Chronic Constriction Sciatic Nerve Injury-induced Neuropathic Pain In Rats

Objective To observe the effect of paeoniflorin on the proliferation and activation of spinal microglia in rats with chronic constriction sciatic nerve injury.Methods 36 cleansing-grade healthy male SD rats were randomly divided into three groups(n = 12): the chronic constriction sciatic nerve injury model group(CCI group),sham operation group(Sham group)and paeoniflorin group(PF group).Rats in the CCI group and the PF group were established with a chronic constriction sciatic nerve injury model in the left lower limb under anesthesia by intraperitoneal injection of 1% sodium pentobarbital 40 mg / kg.The rats in the Sham group only needed to expose and isolate the sciatic nerve without ligation;After modeling,PF was injected intraperitoneally according to the standard of 60 mg / kg per day,and the same volume of normal saline was injected intraperitoneally daily for 14 days after surgery in the Sham and CCI groups.All rats were tested for basal pain threshold at 1d(T0)before surgery,and were injected intraperitoneally with paeoniflorin 3d(T1),7d(T2),10d(T3),and 14d(T4)after surgery.Two hours later,the paw mechanical withdrawal threshold(PMWT)and paw withdrawal thermal latency(PWTL)were measured.After the behavioral test of T4 rats was completed,1% sodium pentobarbital 40 mg / kg was sacrificed after anesthesia and the injured ipsilateral L4-6 spinal cord segment was taken.Six rats from each group were randomly selected to detect the spinal cord by immunofluorescence.Expression of Ionized calcium binding adaptor molecule-1(Iba1),a specific activation marker of dorsal horn microglia,and the remaining 6 were tested for spinal microglia CX3CR1 and p-p38 MAPK by Western Blot.Results 1.Behavioral test results: Compared with the Sham group,PMWT and PWTL in the CCI group were decreased(P<0.001);compared with the CCI group,the PMWT in the PF group was increased,T2(P<0.05),T3(P<0.05)and T4(P<0.01),and PWTL increased,which were T2(P<0.05),T3(P<0.001),and T4(P<0.05).2.Immunofluorescence test results: Compared with the Sham group,the expression of Iba1 in the spinal dorsal horn of the CCI group were increased(P<0.01);compared with the CCI group,the expression of Iba1 in the spinal dorsal horn of the PF group were decreased(P<0.05).3.Western Blot test results: Compared with the Sham group,the expression of CX3CR1 and p-p38 MAPK in the spinal cord of CCI group were increased(P<0.01);compared with the CCI group,the expression levels of CX3CR1 protein in the spinal cord of PF group rats were decreased(P<0.01),p-p38 MAPK protein elevation were decreased(P<0.05).Conclusion The mechanism of paeoniflorin alleviating neuropathic pain may be related to the inhibition of spinal microglia activation.