【作者】 杨弘彦；

【导师】 孙心德；

【作者基本信息】 华东师范大学 ， 生理学， 2002， 博士

【摘要】 本实验室以往的研究表明，在生后发育“关键期”内对大鼠施行单耳堵塞，成年后测定显示，堵塞耳对侧中枢神经元听反应敏感性降低，并伴随相关脑区NMDA受体密度的下降，NMDA受体亚单位mRNA表达减弱。推测NMDA受体与脑听觉功能发育及其可塑性相关。 本实验采用脑区埋管给药技术，在C57B1/6小鼠生后发育“关键期”内，在其左侧大脑听皮层定位、慢性施加NMDA受体NR2B亚单位非竞争性特异拮抗剂MK-801。待成年后，应用行为学方法、常规电生理学方法和形态学方法，考察在发育“关键期”内，听皮层定位、慢性施加MK-801对小鼠脑听觉功能发育的影响。 1、NR2B对听空间方位分辨行为的影响 实验在正常组、单纯手术组和实验组C57B1/6小鼠上进行，应用本实验室自行研制的听空间方位分辨测定装置，研究了在动物发育“关键期”内听皮层定位、慢性施加MK-801对其听空间方位辨别能力的影响。 结果提示，实验组动物建立朝向条件反射所需的训练时间长，成功率低；当取食时间限制为7.5秒内时，即不能建立朝向条件反射，而正常组和手术组动物在此时间限制下能够建立良好的朝向条件反射。在保证相近的全场取食成功率前提下，实验组动物的朝向条件反射反应时较正常组和手术组延长＞65％，且听空间方位角分辨误差较正常组和手术组增大＞210％。正常组和手术组存在取食的优势方位角，在优势方位角范围内，反应时和方位误差明显小于全场的反应时和方位误差；而实验组动物没有取食优势方位，其在各个 方位的反应时和方位误差接近。 实验结果证实，实验组动物听空间方位分辨能力较正常组和手术组动物 明显降低。 2、NRZB对听皮层神经元听觉敏感性发育的影响 实验分别在7只正常组动物、5只手术组动物和6只实验组动物上进行， 采用常规电生理学方法，分别记录了3个组各81个初级听皮层听神经元听反 应，考察了在发育“关键期”内，听皮层定位、慢性施加MK－801对其听觉敏 感性的影响。 结果显示，实验组动物初级听皮层听神经元分布范围较局限，埋管位置 内和埋管位置附近听神经元数量较正常组和手木组明显减少，神经元听反应 中心弥散地分布在记录皮层对测听空间，且有一部分神经元的听反应中心落 在测量方位以外的听空间里，而正常组和手术组初级听皮层神经元听反应中 心集中落在对侧听空间的水平方位20“～60“，垂直方位上方20”～下方 20“的范国内。实验组初级听皮层神经元最佳频率分布在 4～10kHZ，较正常 组和手术组最佳频率分布（5～20kHZ）明显降低。实验组短潜伏期神经元数 量较正常组和手术组减少，阈值也较正常组和手术组明显升高，平均提高 10dB SPL。实验组频率调谐曲线较正常组和手术组增宽，Q＊值降低，锐度明显减 小。实验组听神经元的听空间反应域较正常组和手术组明显增大，其中阈上 sdB声刺激强度时，实验组的听空间反应域平均较正常组和手术组扩大300％ 以上。 结果提示，实验组动物听觉敏感性较正常组和手术组动物明显降低。 2、NRZB对听皮层形态发育的影晌 实验在正常组、手术组和实验组各3只动物上进行，采用快速HE冰冻切 片 Sheehc。染色法，考察了在发育“矢键期”内，听皮层定位、慢性施加 MK－801 对小鼠听皮层神经组织发育的影响。 结果显示，实验组动物听皮层受药侧厚度较正常组和手术组动物明显变 薄，听皮层细胞密度明显减少，存在极显著差异（P＜0．001），非受药侧皮层 较正常组和手术组略有增厚，细胞密度略有增加，存在显著性差异（P＜0．05）， 11 推测可能是动物发育中的一种代偿作用。 以上实验结果提示，NMDA受休在小鼠生后脑神经元听空间敏感性发育中起 重要作用。更多还原

【Abstract】 Previous studies made in our lab indicated that monaural plugging during the critical period of postnatal development would reduce the special sensitivity of the auditory neurons in the contrary auditory cortex of the plugged ear, with the decrease of NMDA receptor density and its subunits expression in the relative cortex of the adult animal. This suggested that NMDA receptor must play a role in the plasticity of brain auditory functional development.In this study, we implanted a pipe on the surface of the left auditory cortex in C57B1/6 mice, during their critical period, then chronically administrated the NMDA receptor 2B subunit antagonist MK-801 though the pipe for 10 days. Using behavioral, electrophysiological and histological method, we studied the influence of chronically administrating of MK-801 during the critical period on the developmentivof auditory function development.1. The influence of NR2B on the behavior of auditory spatial discriminationUsing the food conditioned reflex, we compared the behavior of auditory spatial discrimination among the adult mice of control group, sham group and MK-801 group.The mice in MK-801 group needed more training to establish the food conditioned reflex and longer time (>65%) to complete a reflection, compared to the mice in control group and sham group. The deviation error of auditory spatial discrimination of the MK-801 group was much larger (>210%) than that of the other two groups.The result proved that the auditory spatial discrimination ability of the mice in MK-801 group was much poorer than that in control group and sham group.2. The influence of NR2B on the spatial sensitivity development of auditory cortex neuronsUsing the electrophysiological method, we investigated the spatial sensitivity of auditory cortex neurons of the adult mice in control group, sham group and MK-801 group.The distribution of auditory neurons of MK-801 group was limited in a smaller area of auditory cortex than the other two groups.There were few neurons detected in the area and near the area once implanted the pipe and administrated MK-801 in MK-801 group. The response centers of AC neurons of the mice in MK-801 group were scattered over a wider range of auditory space; the sizes of auditory spatial response area was bigger; the best frequency of AC neurons was lower; the width of tuning curve was wider; and the QndB value was smaller than that of the neurons in the other two groups.The result suggests that the auditory spatial sensitivity of AC neurons of the mice in MK-801 group is much poorer than that of control group and sham group. 3. The influence of NR2B on the development of auditory cortexUsing the histological method, we investigated the influence of NR2B on the development of auditory cortex of the adult mice in control group, sham group and MK-801 group.In MK-801 group, the auditory cortex administrated MK-801 during the critical period was much thinner than the other side of the same mouse, and the cortex of the mice in the other two groups. The cell density of the auditory cortex administrated MK-801 was also much lower than the other side of the same mouse, and the cortex of the mice in the other two groups. And we also found the auditory cortex non-administrated MK-801 during the critical period of themice in MK-801 was a little thicker than the cortex of the mice in the other two groups, while the cell density of the auditory cortex non-administrated MK-801 of the mice in MK-801 group was also a little higher than the cortex of the mice in the other two groups. It might be a kind of functional compensation during the development.The result suggests that NMDA receptor is essential in the development of auditory cortex neurons.In summary, NMDA receptor plays an important role in the postnatal development of auditory spatial sensitivity of brain neuronsin mouse.更多还原