The effects of control on stress-induced gastric erosions: the use of active shuttle-box avoidance learning with yoked controls.

The aim of the present study was to investigate effects of instrumental control on the development of stress-induced gastric erosions by using a shuttle-box paradigm with yoked controls. In Experiment 1 the learning conditions had a reinforcement ratio of only 70% to increase stress during the short-term learning session. No significant differences of the mean cumulative length of gastric erosions between active avoiding and yoked groups were found. Experiment 2 tested three different reinforcement conditions (70%, 90%, 100%) with yoked groups. Again, no significant differences of the mean cumulative length of erosions between active avoiding and yoked control groups were obtained. Instead, the length of erosions decreased with increasing reinforcement. Taken together, the data show that the frequency of unavoided noxious stimuli as a function of the reinforcement schedule can be seen as a major influence on the development of gastric erosions in a shuttle-box paradigm.