Age-related changes in grooming behavior and motor activity in female rats

The influence of hormonal status and the age of the rat on the expression of grooming behavior and motor activity were studied. Grooming, locomotion, and rearing were measured in young (4-months-old), adult (6-8-months-old), and old (18-months-old) female rats, during the estrous cycle. These behavioral performances were influenced by the hormonal changes that occur in young and adult female rats during the estrous cycle. In old rats there were no significant differences among the different days of the estrous cycle. A significant age-related decrease in grooming behavior and motor activity was also found. Locomotion and rearing were the parameters most affected by age. These findings could be related to: (a) the gonadal hormonal status, which appears to be able to modulate behavioral responses; and (b) the age-related changes, which may affect the normal display of these behaviors. The possible role of central peptidergic, cholinergic, and dopaminergic neural systems is discussed.