Effects of previous physical exercise to chronic stress on long-term aversive memory and oxidative stress in amygdala and hippocampus of rats

Since stressful situations are considered risk factors for the development of depression and there are few studies evaluating prevention therapies for this disease, in the present study we evaluated the effect of previous physical exercise in animals subjected to chronic variable stress (CVS), an animal model of depression, on behavior tasks. We also investigated some parameters of oxidative stress and Na+, K+-ATPase activity, immunocontent and gene expression of alpha subunits in amygdala and hippocampus of rats. Young male rats were randomized into four study groups (control, exercised, stressed, exercised + stressed). The animals were subjected to controlled exercise treadmill for 20 min,three times a week, for two months prior to submission to the CVS (40 days). Results show that CVS impaired performance in inhibitory avoidance at 24 h and 7 days after training session. CVS induced oxidative stress, increasing reactive species, lipoperoxidation and protein damage, and decreasing the activity of antioxidant enzymes. The activity of Na+, K+-ATPase was decreased, but the immunocontents and gene expression of catalytic subunits were not altered. The previous physical exercise was able to improve performance in inhibitory avoidance at 24 h after training; additionally, exercise prevented oxidative damage, but was unable to reverse completely the changes observed on the enzymatic activities. Our findings suggest that physical exercise during the developmental period may protect against aversive memory impairment and brain oxidative damage caused by chronic stress exposure later in life.