RESTRAINT STRESS REVERSIBLY ENHANCES SPATIAL MEMORY PERFORMANCE

The effects of restraint stress on performance of a spatial memory tas k, the eight arm radial maze, was examined in rats. When stress was gi ven for 6 h/day for 7 days and performance evaluated days 10-13 post s tress, no effect on performance was noted; however, daily restraint st ress for 13 days caused a small, but significant, enhancement of perfo rmance days 10-13 post stress. Stressed rats performed better than con trols: their number of correct choices in the first 8 visits was highe r than the controls, and stressed rats took fewer total choices to fin ish the maze than controls. Stress-dependent, enhanced performance doe s not appear permanent since further maze testing on days 14 and 15 po st stress showed no differences between the groups. Performance of the stressed rats significantly correlated with their stress-induced, ser um corticosterone levels measured after 6 h of restraint on the last d ay of restraint, day 13 (r = -0.63, P < 0.05); rats with higher levels of CORT took fewer choices to finish the task. Examination of hippoca mpal CA3c pyramidal neurons with Golgi techniques showed no effect of stress on the basal or apical dendritic arbors. Since our previous stu dy showed that 21 days of restraint stress is associated with impaired spatial memory performance (10), these results suggest that the durat ion of stress may differentially affect learning/memory with shorter p eriods of stress serving an adaptive function while longer durations c ausing maladaptive changes.