慢性间歇低氧对幼鼠认知及相关脑区CREB的影响

目的:观察慢性间歇低氧(CIH)对幼鼠认知的影响并探讨其潜在的机制。方法:取八臂迷宫训练成功的SPF级健康雄性SD幼鼠40只,随机分为:间歇低氧2周(2IH)、4周组(4IH),对照2周(2C)、4周组(4C),建立IH幼鼠模型,低氧结束后进行八臂迷宫测试,观察海马和前额叶皮层超微结构变化及cAMP反应元件结合蛋白(CREB)mRNA和磷酸化CREB蛋白的表达。结果:4组幼鼠的记忆错误次数比较均有显著差别(均P0.05);IH各组海马及前额叶皮层神经元均出现早期凋亡和变性,尤以4IH组最为明显,对照组则基本正常;与相应对照组相比,2IH、4IH组幼鼠海马和前额叶皮层CREB mRNA和p-CREB蛋白的表达水平显著降低(均P0.05),且以4IH组最低(均P0.01),差异显著,两对照组之间无显著差异(P0.05)。结论:慢性间歇低氧诱导海马和前额叶皮层神经元超微结构改变,还下调CREB的基因转录和抑制CREB蛋白磷酸化,抑制记忆相关蛋白的合成,这可能是引起学习记忆能力下降的重要机制之一。

Effect of chronic intermittent hypoxia on memory and CREB expression in growing rats

AIM: To observe the alterations in cognition of growing rats exposed to chronic intermittent hypoxia (CIH) and to explore its underlying mechanisms. METHODS: Forty male Sprague-Dawley rats (3-week-old～4-week-old and 80 g to 100 g), which had been trained to complete the 8-arm (4-arm baited) radial maze, were randomly divided into 4 groups: 2-weeek-CIH group (2IH), 4-week-CIH group (4IH), 2-week-control group (2C) and 4-weeek-control group (4C). The intermittent hypoxia model was induced by putting the animals in an intermittent hypoxia cabin. When intermittent hypoxia was terminated, spatial memory of these growing rats was tested by 8-arm (4-arm baited) radial maze task, then, one rat in each group was randomly selected for ultrastructural observation. The hippocampus and prefrontal cortexes of the rats were collected for analyzing the mRNA and protein expression of CREB by RT-PCR and Western blotting, respectively. RESULTS: (1) In the 8-arm (4-arm baited) radial maze task, the results indicated that the rats in the 4 groups displayed significant difference in their performance assessed by three measuremens: the reference memory error, the working memory error and total memory error (P<0.05, respectively). (2) Early apoptosis and destructure of the neurons in the hippocampus and prefrontal cortex were observed under electron microscope in CIH exposed groups, especially in 4IH group, but not detected in 2C and 4C groups. (3) The expression levels of CREB mRNA and p-CREB protein in 2IH and 4IH groups were less than those in 2C and 4C groups in the hippocampus and prefrontal cortex (P<0.05, respectively), especially in the hippocampus of 4IH group (P<0.01). No difference was found within control groups (P>0.05, respectively). CONCLUSION: Exposure to experimentally-induced IH in growing rats is associated with time related spatial memory impairment. Chronic intermittent hypoxia leads to the disorders of neuron ultra-structure in memory related brain regions. It also inhabits the CREB transduction, expression and CREB phosphorylation, decreases the synthesis of the memory related protein. These factors maybe contribute to learning-memory impairment of growing rats exposed to chronic intermittent hypoxia.