Effects of CO insufflation into the colonic lumen on macroscopic findings, mucosal damage score, and wet colon weight after trinitrobenzene sulfonic acid (TNBS)-induced injury. (A) Severe colitis was induced, including hyperemia, edema, thickening, ulceration, and necrosis, in TNBS-treated rats (normal air group). These changes were reduced in rats treated by CO insufflation into the colonic lumen (CO group). (B) The ulcer index was evaluated. *P < 0.01 compared to sham-operated rats. #P < 0.05 compared to rats with TNBS-induced colitis receiving normal air insufflation. (C) The wet colon weight was measured. Data represent the mean ± SEM of 7 rats. *P < 0.05 relative to sham-operated rats. #P < 0.05 relative to rats with TNBS-induced colitis receiving normal air insufflation.