Photomicrographs (hematoxylin and eosin stain, × 100) of distal colon at 2 and 7 d, respectively. A, B: Control group; C, D: Placebo group; E, F: Berberine group; G, H: Aminoguanidine group; I, J: Berberine + aminoguanidine group. At 2 d, histological inflammatory features including mucosal hemorrhage, submucosal edema, and inflammatory infiltration in the lamina propria and the submucosa were observed in the placebo, berberine, aminoguanidine, and berberine + aminoguanidine groups (A, C, E, G, I). At 7 d, there was no marked inflammatory feature compared with the control group (B, D, F, H, J).