脑发育不同阶段丰富环境刺激对缺氧缺血性脑损伤大鼠学习记忆的影响

目的 探讨在不同发育阶段丰富环境刺激对缺氧缺血性脑损伤(hypoxic-ischemic brain injury, HIBI)新生大鼠学习记忆能力的影响.方法 7 d龄SD大鼠通过结扎左侧颈总动脉,吸入8%氧氮混合气,制成HIBI模型,分为干预组(intervention)、非干预组(non-intervention),同时设假手术对照组(sham).其中干预组根据干预开始时间又分为早期干预组(断奶前开始干预)、晚期干预组(断奶后开始干预),分别在断奶前后(生后25 d)开始给予丰富环境刺激,总干预时间为20 d.3个月龄时测定各组学习记忆能力(Morris水迷宫),海马CA1区存活锥体神经元计数评估脑损伤程度,比较不同发育阶段丰富环境干预的效果. 结果 早期干预组学习记忆能力和海马存活锥体神经元数明显高于晚期干预组(P＜0.01).早期干预组与假手术组差异无显著意义(P＞0.05).结论 断奶前开始给予丰富环境干预较断奶后能明显改善HIBI大鼠学习记忆能力,减轻HI后海马病理损伤程度可能是其原因之一.

Effect of environmental enrichment at different development stages on learning and memory abilities in hypoxia-ischemic brain injured postnatal rats

Objective To observe the effects of environmental stimulation at different stages of development on postnatal rats with hypoxia-ischemic brain injury (HIBI). Methods HIBI postnatal SD rats models were established by dissecting and ligating the left common carotid artery, and after 2 h of recovery, exposing to 8% oxygen-92% nitrogen gas mixture for 2 h. The HIBI rats were randomly divided into early intervention groups, late intervention group, non-intervention group. Intervention group were kept in enriched environment before or after weaning for 20 d. Non-intervention group and control group were kept in a standard environment. Space learning and memory were tested with Morris water maze. Results The ability of space learning and memory in early intervention group was better than that in late intervention group (P<0.01). The number of the survival pyramid neurons of hippocampus CA1 section of early intervention group was much more than that of late intervention group (P<0.01). There was no marked difference between early intervention group and sham group. Conclusion The damage in the left hippocampus of early intervention group is decreased obviously, and the ability of learning and memory is promoted while late intervention group has quiet effects, which indicating that environmental enrichment at pre-weaning improves learning and memory of HIBI rats much more than that at post-weaning. Changes of pathology in their hippocampus are possibly associated with the effects of environment.