CPZ诱导精神分裂症样模型小鼠海马脱髓鞘改变与行为学变化及其相关性的研究

Demyelination in the hippocampus and its correlation with altered behaviors of the cuprizone-induced mouse model of schizophrenia

摘要:

目的：研究双环己酮草酰二腙（cuprizone，CPZ）诱导 C57BL/6小鼠建立的精神分裂症样模型小鼠海马内有髓神经纤维体积改变及其与行为学改变之间的关系。方法：19只雄性 6 周龄小鼠，随机分为实验组（9只）和对照组（10只），实验组用含 0.2%（质量分数百分比，w/w）CPZ的混合鼠饲料饲喂 6 周，建立精神分裂症样小鼠模型；对照组用标准鼠饲料饲喂 6 周。运用旷场实验、高架十字迷宫实验、Morris水迷宫实验、转棒实验和探孔实验测试行为学改变；髓鞘碱性蛋白（myelin basic protein，MBP）免疫组化染色及透射电镜定性观察髓鞘结构变化；体视学方法测量并计算海马总体积及海马内有髓神经纤维体积；统计学方法分析行为学改变与海马内有髓神经纤维体积改变之间的关系。结果：与对照组相比，实验组小鼠体质量下降，差异具有统计学意义（P<0.05）；行为学实验结果表明：实验组小鼠存在异常的焦虑行为（P=0.018）及空间认知能力障碍（P=0.037），但运动能力（P=0.443）、探索习性（P=0.306）及学习记忆能力未见受损（P=0.462）；MBP免疫组化染色发现海马区域免疫阳性染色变浅；透射电镜定性观察发现海马内有髓神经纤维存在脱髓鞘改变；体视学定量测定发现，实验组小鼠海马总体积未发生显著性改变（P=0.955），而海马内有髓神经纤维体积减小（P=0.009）；统计学相关分析发现，闭臂路程百分比和海马内有髓神经纤维体积呈正相关（rs=0.83，P=0.003），开臂路程百分比和海马内有髓神经纤维体积呈负相关（rs=-0.65，P=0.043）。结论：进一步证实 CPZ模型小鼠可以出现类似精神分裂症样症状的行为学改变及海马内有髓神经纤维存在脱髓鞘改变，并且发现海马内有髓神经纤维体积和行为学表现间具有一定的相关性。

Abstract:

Objective：To investigate the correlation between changes of the volume of the myelinated nerve fibers in mouse hippocam－pus and altered behaviors with a novel schizophrenia-like animal model which was established by treating C57BL/6 mice with cupri－zone（CPZ）. Methods：Totally 19 male C57BL/6 mice were randomly divided into experimental group and control group. Experimental mice received powdered rodent chow containing 0.2% CPZ for 6 weeks to establish a schizophrenia-like mouse model，while control mice were fed with standard rodent chow for 6 weeks. Open field test，elevated plus maze test，Morris water maze test，turn-club test and hole board test were used to estimate behavior changes. Anti-myelin basic protein（MBP） immunohistochemistry stain－ing and transmission electron microscope were used to investigate the structure changes of myelin sheaths. Volume density and total volume of the myelinated nerve fibers in the hippocampus were investigated with the stereological methods. Correlation between altered behaviors and changed myelinated nerve fibers in the hippocampus was estimated with correlation analysis. Results：Mean weight was significantly decreased in experiment group than in control group（P<0.05）.Behavior test results indicated that nervous re－sponse and spatial cognitive ability of experimental mice was significantly worse than those of control mice（P=0.018，P=0.037），while action ability，exploration ability and working memory of experimental mice were not significantly different from those of control mice（P=0.443，P=0.306，P=0.462）. MBP positive nerve fibers in the hippocampus were apparently fewer than in experimental mice than in control mice. Demyelination of the myelinated nerve fibers in the hippocampus was observed under transmission electron microscope. Volume of hippocampus of experimental mice was not significantly changed compared with that of control group（P=0.955），while total volume of the mylinated nerve fibers in the hippocampus of experimental mice was significantly less than that of the control mice（P=0.009）. Correlation analysis results suggested that the close-arm distance rate was significantly and positively correlated with volume of the myelinated nerve fibers in the hippocampus（rs=0.83，P=0.003），while the open-arm distance rate was negatively correlated with volume of the myelinated nerve fibers in the hippocampus（rs=-0.65，P=0.043）. Conclusions：The study further demonstrates that CPZ-treated mice display schizophrenia-like behavior changes and mylinated nerve fibers in its hippocampus undergo pathological change of demylination. Moreover，present results indicate that changed volume of the mylinated nerve fibers in the hippocampus is correlated with altered behaviors.