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| Establishment of young mice model of excessive learning and training and its impact on cognition |
| ZHANG Yijing1,2, XU Jian1,2 |
| 1. MOE-Shanghai Key Lab of Children's Environmental Health, Xinhua Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200092, China；2. International Peace Maternity & Child Health Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200030, China |
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Abstract Objective To investigate the establishment of young mice model of excessive learning and training and the effects on cognitive development in young mice. Methods The 25-day-old C57BL/6 mice were randomly divided into four groups depending on gender and whether they were excessively trained (female/male experimental and control groups). The animal model was established based on the classical Morris water maze. The effect of excessive learning and training on spatial memory was evaluated by the place navigation test and probe test. Then the novel object recognition and hematoxylin-eosin staining (H&E) were performed to investigate the impacts of excessive learning and training on recognition memory and hippocampal appearance of the young mice. Results Before the training, the swimming speed and the escape latencies of the four groups showed no significant differences (P>0.05). After excessive training, the female/male experimental mice's escape latencies significantly decreased compared to the counterpart controls (P<0.000 1 for both genders). In the probe test, the platform-crossing times of the male experimental group slightly decreased compared to those of the male control group while the platform-crossing times of female experimental mice slightly increased compared to those of the female control mice, and the differences were non-significant (P>0.05). In the novel object recognition test, the male experimental group spent less time on the new object (relative to the time spent on the old object) 1 h after excessive training compared to the male control group and the recognition memory impairment was observed 24 h after excessive training (P>0.05). The results of H&E suggested that, in the male experimental group, hippocampal neurons were poorly organized with a shrunken appearance, and more degeneration of neurons in hippocampal CA1 region was observed than that in the male control group. Conclusion Excessive learning and training during developmental stages may impair the cognitive functions and exploration ability, especially in the male mice. The hippocampal impairment may be one of the possible mechanisms underlying the cognitive impairment.
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