The influence of food consumption and running activity on the activity-stress ulcer in the rat.

Rats housed in activity cages and fed 1 hour daily died before the end of the 21-day experimental period and revealed extensive ulcers in the glandular stomach, whereas food-yoked control rats, not housed in activity cages, did not die and were ulcer-free. Rats demonstrating high running-activity levels under ad lib feeding conditions subsequently revealed a higher incidence of lesions as compared to low-activity rats. Attempts to attenuate activity and lesion incidence by reversing the light-dark cycle failed, but the higher mortality level in rats under the reversed light-dark condition was related to higher activity levels in these rats. Young rats with high activity levels died sooner and had ulcers when compared to older rats with low activity levels. These results suggested that running activity, and not reduced food intake, was critically involved in the development of the activity-stress ulcer.