Relationship between running activity rhythm and the development of activity-stress ulcer in rats

In the present study, the relationship between the development of activity-stress (A-S) ulcer and the behavioral and physical changes of rats with the A-S paradigm was investigated. We applied the endoscopic technique to establish the A-S ulcer as a model for studying the therapeutic or healing process of ulcers. Male and female rats were subjected to daily 1 hr feeding in the light (L)-phase (09:00-10:00) or in the dark (D)-phase (21:00-22:00). Prior to peak-revolution of running-activity, ulcer occurred earlier in the L-phase feeding group than in the D-phase feeding group. The ulcer development was accompanied with a change in the circadian rhythm of running-activity; e.g., the running-activity of the L-phase was higher than that of the D-phase. This phenomenon was more marked in the L-phase feeding group than in the D-phase feeding group. In addition, the ulcer development was closely related to body weight loss. No sex differences were found in these phenomena. The results suggest that change in the circadian rhythm of running-activity, body weight loss and high running-activity are important variables for predicting the A-S ulcer production, avoiding the need to kill the animals to determine ulcer formation.