Interactions amongst factors which influence severity of gastric ulceration in rats.

A number of factors have previously been demonstrated to influence the severity of stress-induced gastric ulceration in rats, including prior exposure to pre-shock and allowing animals a post-stress rest or recovery period. The primary purpose of this experiment was to investigate how one of these factors might modulate the expression of the other. Animals were pre-exposed to either signalled or unsignalled shock (using "learned helplessness" parameters), or no shock. They were later subjected to 2 hours restraint-in-water (immersion) stress, or appropriate handling control procedures. Half of the animals were sacrificed immediately on removal from the water-restraint, and half were sacrificed after a 2 hour recovery period in their home cages. Analysis of the severity and number of glandular stomach lesions indicated that animals subjected to the pre-shock exhibited greater ulceration than unshocked animals, as long as no post-stress rest period was allowed. Additionally, the effect of post-stress rest was masked by experience with pre-shock. This reciprocal modulation of treatment influences may offer suggestions for understanding discrepancies in the literature on the effects of these two modulating variables.