Decreased anxiety levels related to aging

The present experiment investigated the effects of aging on emotional behavior, without concomitant influences from any previous behavioral manipulation apart from weighing the rats. Anxiety-related behaviors were measured in the elevated plus-maze (EPM). Performance in the open field (OF) was also assessed to control for any effect of aging on exploratory behavior that could account for changes in emotional behavior. Fifty-two naive male Wistar rats of 3 (3MO), 17 (17MO), or 24 (24MO) months, were submitted to two sessions (5 min each) of EPM, followed by two sessions (2 min each) of OF, on 4 consecutive days. The main emotional indices (open arm entries, ratio of open arm entries to total entries, time spent in open arms, ratio of time in open arms to time in four arms, open arm ends, and head dips) measured in the EPM indicated a lower level of anxiety in aged (24MO) than in young (3MO) rats, whereas middle-aged (17MO) rats showed intermediate values between those of 3MO and 24MO rats; 3MO rats showed higher general motor activity (number of rearings in closed arms of EPM and in OF, and higher number of areas crossed in OF) than 17MO and 24MO rats. We conclude that aging is associated with a decrease in anxiety and in general motor activity.