Animals and SNI model

Adult male Sprague–Dawley (SD) rats (6 weeks of age, 160–200 g) were obtained from the Institute of Experimental Animals of Sun Yat-Sen University, and were housed individually with access to food and water ad libitum in a room maintained on a 12 h/12 h light/dark cycle. The temperature and humidity were kept at 24 ±  ℃ and 50–60%, respectively. All experimental procedures were approved by the Local Animal Care Committee and were performed in accordance with the guidelines of the National Institutes of Health on animal care and the ethical guidelines. Efforts were made to minimize the suffering and the number of rats used.

Spared nerve injury (SNI) was performed as described by Decosterd and Woolf [28]. Under isoflurane (4%) anesthesia, three peripheral branches of the sciatic nerve of the left hind limb were exposed. The common peroneal and the tibial nerves were ligated and cut (2 mm sections removed), and the sural nerve was kept intact. After that, the surgical incision was sutured in two layers. For the sham procedure, three peripheral branches of the sciatic nerve were exposed without any nerve damage.