Emotional disorders and memory deficits in senescence-accelerated mice, SAMP8 and SAMP10

Abstract

The senescence-accelerated mouse (SAMP8) showed age-related deficits in avoidance and spatial learning tasks, and also exhibited reduced anxiety-like behavior in tests involving food neophobia, an elevated plus-maze and punished water-licking. The emotional change in SAMP8 was considered to be closely related to the deficits in the learning tasks. Aged SAMR1 showed similar behavioral changes to those in SAMP8 mice, indicating that some of the behavioral changes in SAMP8 may be derived from accelerated aging. SAMP10 mice also showed learning impairment in the avoidance tasks, although the impairment was less than that in SAMP8 mice. SAMP10 exhibited marked behavioral depression when subjected to a tail suspension test or forced swimming test. Thus, the SAMP10 strain may be useful for studying age-related behavioral depression and reduced spontaneity. SAMP8 and SAMP10 also exhibited marked disruption of the circadian rhythms of spontaneous motor activity (SMA) and drinking behavior, and bright light stimulation ameliorated the abnormal circadian rhythms in SAMP8. These findings suggest that SAMP8 and SAMP10 are also valid animal models for age-related disorders of learning and memory, emotional behavior and circadian rhythms in elderly humans and in those with senile dementia.