Male C57BL/6 mice aged 8-12 weeks, weighing about 25 g, were purchased from Shanghai Experimental Animal Center of China. The mice were anesthetized with isoflurane. The abdomen area was disinfected after shaving. A 1 cm midline incision was made on the lower abdomen skin to expose the cecum. A 5-0 silk thread was used to ligate the midpoint between the distal pole and the bottom of the cecum. A 21 g needle was used to penetrate the cecum twice from the mesenteric toward the antimesenteric direction. After the wound was sutured, 0.25% ropivacaine was injected subcutaneously for postoperative analgesia. The mice were immediately resuscitated by injecting prewarmed normal saline 1 ml subcutaneously.