Effects of Predator-Induced Stress and Age on Working Memory in Rats

The effects of age and predator-induced stress, by exposing rats to a cat, were examined during subsequent testing of spatial working memory. Male rats (3 months and 20 months of age) were trained on a spatial delayed-alternation task using an elevated T maze. After subgroups were given intermittent protected-exposure sessions over a 3-day period to cats or to a control condition, they were tested on the working memory task. The old rats took more trials to reach training criterion. Overall, both stress-exposed groups exhibited a decline in accuracy 24 hr later and recovered completely during the subsequent test sessions. Surprisingly, young stressed rats showed significantly greater decrements in accuracy than old stressed rats. However, exposure to the stressor resulted in decreases in response speed that were comparable for both age groups. These findings are discussed in terms of possible changes in glucocorticoids, plasma corticosterone, and endogenous opioids that are known to be affected by age and stress and have been shown to influence spatial working memory.