Chronic Constriction Injury Model

The rat model of neuropathic pain by unilateral ligation of sciatic nerve was performed in rats as described earlier (Bennett and Xie, 1988). Briefly, SD rats were anesthetized by isoflurane delivered using an anesthetic machine. The right common sciatic nerve was dissected, exposed, and ligated at the level of the midthigh using 4 chromic gut (4-0) ties, separated by a 1 mm interval. After ligation, the wound was sutured and the rats were allowed to recover. With the sciatic nerve ligated rats, only those with marked unilateral allodynia to mechanical stimulation (hind limb withdrawal thresholds in the ipsilateral side/contralateral side <0.75) and with no major motor impairment were selected for further studies. The withdrawal thresholds of ipsilateral hind limbs were measured using the procedures described below. On the 9th day after surgery, i.p. AMG was administered 40 min before Ro5-4864 or koumine injection, and the mechanical withdrawal threshold (MWT) was determined 50 min after the last injection. Ro5-4864 and AMG were dissolved in DMSO and diluted in sterile physiological saline (0.9% NaCl), and the final concentration of DMSO was 5%. Koumine was dissolved in sterile physiological saline (0.9% NaCl) directly, and then diluted to the specified concentration. The mock vehicle group was injected with 5% DMSO in saline.