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Constitutive differences in glucocorticoid responsiveness are related to divergent spatial information processing abilities

The stress response facilitates survival through adaptation and is intimately related to cognitive processes. The Morris water maze task probes spatial learning and memory in rodents and glucocorticoids (i.e. corticosterone in rats) have been suggested to elicit a facilitating action on memory formation. Moreover, the early aging period (around 16-18 months of age) is susceptible to stress- and glucocorticoid-mediated acceleration of cognitive decline. In this study, we tested three lines of rats selectively bred according to their individual differences in corticosterone responsiveness to repeated stress exposure during juvenility. We investigated whether endogenous differences in glucocorticoid responses influenced spatial learning, long-term memory and reversal learning abilities in a Morris water maze task at early aging. Additionally, we assessed the quality of the different swimming strategies of the rats. Our results indicate that rats with differential corticosterone responsiveness exhibit similar spatial learning abilities but different long-term memory retention and reversal learning. Specifically, the high corticosterone responding line had a better long-term spatial memory, while the low corticosterone responding line was impaired for both long-term retention and reversal learning. Our modeling analysis of performance strategies revealed further important line-related differences. Therefore, our findings support the view that individuals with high corticosterone responsiveness would form stronger long-term memories to navigate in stressful environments. Conversely, individuals with low corticosterone responsiveness would be impaired at different phases of spatial learning and memory.