4.3. A Rat Model of Spared Nerve Injury (SNI)

After rats were adapted to the surrounding for 5 days, the rat model of spared nerve injury (SNI) was established according to the method described in previous study [28]. Briefly, rats were anesthetized with isoflurane (C002170901, YiPin Pharmaceutical, Shijiazhuang, Hebei, China) at a concentration of 2–3%. The left lateral sciatic nerve and its trifurcations (three terminal branches including sural, common peroneal and tibial nerves) were exposed. The left common peroneal and tibial nerves were tightly ligated with a 4-0 silk thread, being sectioned distal to the ligation with removal of 2–4 mm of the distal nerve stump, and keeping the sural nerve intact. The skin and muscle of rats were closed under sterile condition. Only rats that developed pain hypersensitivity were applied in this experiment. While the sham-operation rats were performed with all identical surgery protocols except that only exposing the tibial and peroneal, the common nerve was not ligated and cut.