新生大鼠缺氧缺血性脑损伤远期行为学和超微结构改变

Long-term behavioral and ultrastructural alterations following hypoxic-ischemic brain damage in neonatal rats

摘要:

目的：建立新生大鼠缺氧缺血性脑损伤（HIBD）模型，观察远期行为学及超微结构改变。方法：60只7日龄新生Sprague-Dawley大鼠随机分为HIBD组和假手术组，每组30只。生后5周进行Morris水迷宫试验及感觉功能测试；取脑组织切片行尼氏染色计数神经元数目；取皮层、海马行透射电镜，观察突触结构，测量突触后致密区（PSD）厚度及活性区长度，并与行为学结果进行相关分析。结果：Morris水迷宫试验中，HIBD组大鼠寻找平台潜伏期时间明显长于假手术组（P<0.05）；HIBD组大鼠穿越平台次数较假手术组少（P<0.05）。感觉运动功能试验中，HIBD组测试结果明显差于假手术组。尼氏染色提示HIBD组神经元数目明显减少（P<0.01）。电镜显示HIBD组大鼠突触数量减少，PSD厚度及活性区长度变薄变短。HIBD组大鼠PSD厚度与Morris水迷宫试验寻找平台潜伏期时间呈负相关（r=-0.861，P<0.01），与三项感觉功能评估得分之和亦呈负相关（r=-0.758，P<0.05）。结论：缺氧缺血可致新生鼠远期神经元减少和超微结构损伤，造成远期行为学功能障碍。

Abstract:

OBJECTIVE: To study long-term behavioral and ultrastructural alterations in a hypoxic-ischemic brain damage (HIBD) model of neonatal rats. METHODS: Sixty seven-day-old Sprague-Dawley rats were randomly subjected to unilateral carotid artery ligation followed by hypoxic exposure (HIBD group) or sham operation (n=30 each). A battery of behavioral tests, including Morris water maze test and sensorimotor tests, were performed at a postnatal age of 5 weeks. Nissl staining was used for counting neurons. Transmission electron microscopy was used for observing synapse structures and measuring the thickness of the postsynaptic density area and the length of the postsynaptic active area. The correlations of histological changes with the results of behavioral tests were evaluated. RESULTS: The HIBD group showed a significantly longer escape latency (P<0.05) and a lower frequency of original platform crossing (P <0.05) in the Morris water maze test compared with the sham operation group. The sensorimotor function test showed that the sensorimotor function in the HIBD group was worse than in the sham operation group. Nissl staining showed that the number of neurons in the HIBD group was significantly reduced (P <0.01) compared with the sham operation group. Transmission electron microscopy showed that synapses were significantly reduced in number, and that the thickness of the postsynaptic density area and the length of the postsynaptic active area were reduced in the HIBD group. The thickness of the postsynaptic density area was negatively correlated with escape latency in the Morris water maze test (r=-0.861, P<0.01), and also negatively correlated with the total score of sensorimotor function tests (r=-0.758, P<0.05) in the HIBD group. CONCLUSIONS: Hypoxia ischemia can lead to neuron loss and ultrastructure damage, resulting in long-term deficit of behavioral functions in neonatal rats.