Effects Of Sinomenine On Oxidative Stress In Spinal Cord In A Rat Model Of Neuropathic Pain

Objective To evaluate Sinomenine(SIN) efficacy of neuropathic pain and effects of sinomenine on the neuronal apoptosis in spinal dorsal horn and oxidative stress in spinal cord in a rat model of neuropathic pain(NP), and to explore the role of oxidative stress in neuronal apoptosis, whether sinomenine’s analgesic mechanism works by inhibiting the oxidative stress in spinal cord and neurons apoptosis in spinal dorsal horn..Methods Take adult male Wistar rats 108, weighing 180-220g,6-8 weeks of age, by using the random number table Wistar rats were divided into three groups (n=36):sham group (S group) Sinomenine injection group (SIN group) and neuropathic pain group (CCI group). S group’s sciatic nerve were only isolated but not ligated, CCI group and SIN group were prepared neuropathic pain model in Wistar rats through chronic sciatic nerve crush injury. Sinomenine 40mg/kg was injected in SIN group once a day, the injection time was from rats’s awake after surgery utill one day before sacrificed of these rats, S group and CCI group were injected the same capacity (1.6 ml/kg) saline at the same time. One day before operation(T0) and 3days(T1)、 7days(T2)、14 days(T3) after operation respectively thermal pain threshold (TWL) and mechanical paw withdrawal response threshold (MWT)were measured, after measured of pain threshold on T1、T2 and T3 12 rats were were sacrificed in each group after operation, six rats’s L4-6 spinal cord tissue were taken out for determination of neuronal apoptosis in spinal dorsal horn (by TUNEL), the other six rats’s L4-6 spinal cord tissue were used for determination of MDA content、SOD activity(by spectrophotometry) in spinal cord.Results Compared with group S, MWT was significantly decreased,TWL was shortened,the neuronal apoptosis rate was increased,MDA content was increased and SOD activity was decreased at T1-3 in groups CCI and SIN (P<0.05).Compared with group CCI,MWT was significantly increased,TWL was prolonged,the neuronal apoptosis rate was decreased,MDA content was decreased and SOD activity was incresed at T1-3 in group SIN(P<0.05).SOD activity and apoptosis was negatively correlated(r=-0.973,p<0.01),MDA content and apoptosis was positively correlated (r=0.929,p<0.01).Conclution Sinomenine can reduce neuropathic pain, Sinomenine can reduce spinal cord dorsal horn neuronal apoptosis and inhibit spinal cord’s oxidative stress of neuropathic pain rats. Sinomenine’s analgesia mechanism may be inhibiting oxidative stress in spinal cord and then to reduce neuronal apoptosis in the spinal dorsal horn.