Neuropathic Pain Model Induced by Spinal Nerve Ligation

Spinal nerve ligation (SNL) surgery was performed to induce neuropathic pain model as previously reported.^{20 (link)} Briefly, the mice were anesthetized with sodium pentobarbital and barbered along the back with skin sterilization by chlorhexidine. After removal of L6 transverse process to expose the ventral ramus of the L4 and L5 spinal nerves, the L5 spinal nerve was identified and tightly ligated with 6-0 silk threads without damage to the other nerves. Mice were then randomly divided into 5 groups (n = 10 in each group). In the control group, the left L5 spinal nerve was isolated without ligation. Group 2 was conducted with SNL treatment. The other groups served as SNL + oleanolic acid (OA, >97% purity) (Sigma, St. Louis, MO, USA) groups wherein the mice were separately injected (i.p.) with 2 mg kg⁻¹, 5 mg kg⁻¹, and 10 mg kg⁻¹ of oleanolic acid after SNL surgery for 5 consecutive days.