Sex differences in spatial and non-spatial Y-maze performance after chronic stress.

Chronic restraint is known to alter hippocampal CA3 dendritic morphology and spatial memory in male rats. The present study examined whether female rats, which exhibit different anatomical adaptations to chronic stress than those of males, would also show spatial memory impairments. Male and female Sprague-Dawley rats were restrained for 6 h/day for 21 days, a time frame previously demonstrated to cause hippocampal CA3 dendritic atrophy. The day after the last restraint session, rats were tested on a Y-maze, a habituation task that can be used to assess spatial memory. Chronic stress impaired Y-maze performance in both sexes without affecting levels of locomotion as measured by total arm entries in the first minute. However, Y-maze performance of stressed females improved in 2-5 min when chronically stressed males continued to show poor Y-maze performance. The enhanced Y-maze performance of chronically stressed females occurred when total arm entries were higher compared to the entries made by males. Therefore, correlations were performed between total arm entries and spatial memory in 1 and 2-5 min. In the first minute when control females demonstrated functional spatial memory, female controls with the lowest locomotor levels exhibited the best performance. The correlations for stressed females were not significant, and neither were the correlations for any group in 2-5 min. Overall, these results show important sex differences in response to chronic stress with females exhibiting an ability to recover quickly from deficits in Y-maze performance.