The relationship between behavioral change and hippocampal lesion was
studied in ddY male mice, at 4.5, 20, 40 and 60 weeks of age. In passi
ve avoidance response, the aging mice (40 and 60 weeks of age) showed
shorter latency than young mice (4.5 weeks of age). The degenerated py
ramidal cells were more numerous after 40 weeks of age in the CA3 than
CA1. The mean incidence of the degenerated pyramidal cells in the CA3
was 20.8% at 60 weeks of age. In 71.9% of mice, impairment of passive
avoidance response was associated well with hippocampal lesions. Thes
e results indicate that the hippocampus plays some role in the memory
in mice. The ddY mice may be possible to use as models for reversible
hippocampal lesion.