POI induction and Intestinal transit test

Mice were randomly assigned into 3 groups with at least 6 mice in each group: (1) Control group (con): no surgery; (2) Sham group (sham): laparotomy with intestinal exposure but without further manipulation; (3) POI group (POI): laparotomy with intestinal manipulation. POI was induced according to the method of Li et al. ⁶. Briefly, mice were anesthetized with an intraperitoneal application of (2.5µl/g, i.p.) Midazolam, Medetomidin and Fentanyl. To relieve pain, Novalgin (1.5µl/g, s.c.) was administrated before surgery. After midline-laparotomy, the small intestine was mobilized out of the abdominal cavity and put on a small wet gauze. Then, the small intestine was manipulated by rolling sterile wet cotton swabs along the intestine for 5 min. For sham-operated animals, the small intestine was only taken out of the abdominal cavity and put on a wet gauze for 5 min without further manipulation. After surgery, the mice received an antagonist (8.5µl/g, i.p.) which contained Atipamezol, Naloxon and Flumazenil. After 24 h of surgery, mice received a gum arabic suspension with active carbon by gavage (0.1 ml/10 g). 20 min later, the blood was collected by heart puncture under anesthesia. Then, the mice were sacrificed and the intestine was separated from the abdominal cavity for the measurement of the distance that carbon has been pushed forward and the whole length of the small intestine. The intestinal transit was calculated with equation (carbon passed distance / whole length of small intestine x 100) as described elsewhere ⁷. Then ileac and colonic species were evenly divided into 1cm start from the cecum and arranged for the different detection. 5 Peyer's patches (PPs) in the small intestine were collected from each mouse. For the detection of histamine and toluidine blue staining, except for 24 h, blood and colonic segments were also collected after 12 h and 48 h of surgery.