Behavioral impairments of the aging rat.

Several disturbances occurring during aging of humans and rodents alike stem from changes in sensory and motor functions. Using a battery of behavioral tests we have studied alterations in performance with advancing age in female and male rats of some frequently used strains. In parallel, we collected survival and body weight data. The median survival age was similar for female and male Sprague-Dawley rats, inbred female Lewis and outbred male Wistar rats (29-30 months). In contrast, male Fisher 344 had a significantly shorter median life span. During aging there is a gradual decline in locomotor activity and explorative behavior while disturbances of coordination and balance first became evident at more advanced age. In old age, also weight carrying capacity, limb movement and temperature threshold were impaired. While whole body weight continues to increase over the better part of a rats' life span, the behavioral changes in old age associated with a decrease in both total body weight and muscle mass. Dietary restriction increases median life span expectancy; retards the pace of behavioral aging and impedes sarcopenia. Housing in enriched environment did not improve the scoring in the behavioral tests but tended to increase median life span. Finally, there was an agreement between behavioral data collected from longitudinal age-cohorts and those obtained from multiple age-cohorts.