Impairment of learning and memory in rats caused by oxidative stress and aging, and changes in antioxidative defense systems.

To elucidate the influence of oxidative stress on the brain functions during aging, the cognitive performance ability of rats was assessed by using the water-maze test as an oxidative stress before and after hyperoxia. Young rats showed significantly greater learning ability than both old rats and vitamin-E-deficient rats. Although the memory functions of all rats were Impaired after oxidative stress, the memory retention of young rats was greater than those of other groups. After the stress, none of the rats recovered their learning ability. During aging and through hyperoxia, the release of acetylcholine from nerve terminals was remarkably decreased. Instead, thiobarbituric acid reactive substance (TBARS) contents in rat hippocampus and cebral cortex, and their synaptic membranes, were significantly increased during aging and by oxidative stress. The antioxidative defense system in rat brain was also changed by the stress. These results suggest that oxidative stress may contribute to learning and memory deficits following oxidative brain damage during aging.