Effect Of Paeoniflorin On Pain Behavior And Activation Of Spinal Astrocytes In Rats With Neuropathic Pain

Objective To establish the neuropathic pain model of rats with chronic constriction injury（CCI）,to investigate the effect of paeoniflorin on pain behavior and activation of spinal astrocytes in neuropathic pain rats.Methods 48 cleansing-grade male SD rats weredivided into 3 groups by random Digital scale method:Sham group（sham group）,model group（CCI group）,CCI+paeoniflorin（PF group）.In group CCI and group PF,sciatic nerve ligation was performed on the left side of the rats,and the sciatic nerve in group Sham was not ligated.The rats in PF group were injected with paeoniflorin（60mg/kg）every day,and the rats in sham group and CCI group were injected with saline of equal volume every day,14 consecutive days.Thermal Withdrawal Latency（TWL）and Mechanical Withdrawal Threshold（MWT）after 2h of administration,were measured at 1 day before operation（T₀）,1 day（T₁）,4 days（T₂）,7 days（T₃）and 14 days（T₄）after operation respectively.4 rats in each group were randomly selected.After pain behavior test of T_2,T₃and T₄rats,L4-6 spinal cord segments were taken from anaesthetized rats,and the expression level of GFAP in astrocytes in dorsal horn of spinal cord was detected by Western blot.In addition,at the time of T₄,4 rats were randomly selected from each group under deep anesthesia,the chest cavity was dissected to fully expose the heart,and 4%paraformaldehyde was infused.The fixed L_4-6spinal cord segments were taken for immunohistochemical staining to determine the dorsal spinal cord Number of horned astrocytes.Results 1.There was no significant difference in TWL and MWT between each group（P>0.05）.Compared with the Sham group,at the time points T₁,T₂,T₃,and T₄,the CCI group and the PF group decreased in MWT,shortened TWL,and the difference was statistically significant（P<0.05）;Compared with the CCI group,MWT increased and TWL prolonged in the PF group at T₁,T₂,T₃,and T₄,and the difference was statistically significant（P<0.05）;2.Western blot results:Compared with the Sham group,the expression of GFAP in CCI group and PF group was up-regulated at T₂,T₃,and T₄time points（P<0.05）;Compared with the CCI group,the expression of GFAP was decreased in the PF group at T₂,T₃,and T₄（P<0.05）;3.Immunofluorescence results:At T₄,compared with the Sham group,the spinal cord astrocytes in the CCI group were significantly activated and the number of cells was increased（P<0.05）.Compared with the CCI group,the spinal cord in the PF group was star Glial cell activation was weakened and the number of cells decreased（P<0.05）.Conclusion1.Paeoniflorin reduced the pain behavior of neuropathic pain rats;2.Paeoniflorin may reduce neuropathic pain by inhibiting the activation of astrocytes in spinal dorsal horn.