Partial Infraorbital Nerve Ligation Model

ICR male mice weighing 26 g–30 g were provided by the Experimental Animal Center at Nantong University. Tlr8^−/− mice were developed by Cyagen Co. (Suzhou, China). Tlr7^−/− mice were purchased from the Jackson Laboratory (stock number 008380). All mice were housed in standard clear plastic cages under controlled ambient temperature (22 °C–24 °C) with a reversed 12:12 h dark/light cycle, and allowed ad libitum access to water and food. The experimental and surgical procedures were reviewed and approved by the Animal Care and Use Committee of Nantong University. Animal treatments were performed in accordance with the guidelines of the International Association for the Study of Pain.
The pIONL surgery was as described by Zhang et al. [24 (link), 25 (link)]. In brief, mice were anesthetized with sodium pentobarbital (40 mg/kg–50 mg/kg, i.p.), and then the oral cavity was opened to locate the tendon of the left masseter muscle on the upper wall of oral cavity in the supine position. In front of the tendon, an incision (1 mm) was made to expose the infraorbital nerve. The TNP model was established by ligating one-half of the infraorbital nerve (ION) with 6-0 silk suture. The mucous membrane of the incision was closed with Tissue Adhesive (Vetbond; 3M, USA). The sham operation comprised an incision on the mucous membrane without damaging the ION.