宫内生长受限大鼠海马突触稳态可塑性的动力学特征及机制研究

Synaptic homeostatic plasticity is an important mechanism developed to maintain the stability of the neural circuit in recent years. In order to adjust the activity of the neural circuit automatically to a certain physiological range in the neural networks and maintain the central excitability, both excitatory and inhibitory synapses regulate the kinetic characteristics of the neural networks by homeostasis model.The recent experiments confirmed that field excitatory postsynaptic potentials decreased from hippocampal Schaffer collateral to area CA1 pathway under intrauterine growth restriction model.The above result suggests that hippocampus neural networks in CA1 area under intrauterine growth restriction may exist imbalance process in synaptic homeostatic plasticity. The present project will be carried out in hippocampal CA1 pyramidal neurons. Patch clamp technology is used as one of the main methods. The kinetic characteristics of synaptic homeostatic plasticity will be recorded. Furthmore, signal transduction pathways about synaptic homeostatic plasticity will also be explored in CA1 pyramidal neurons. In order to explain the mechanisms of synaptic homeostatic plasticity in CA1 pyramidal neurons, receptor expression will be explored by immunohistochemical staining method.Calcium ion concentration in CA1 pyramidal neurons and change mechanisms will be further exhibited by fluorescent imaging method . The aim to study the change and mechanisms of hippocampal synaptic homeostatic plasticity under intrauterine growth restriction is to promote the homeostatic improvement of neural network by regulating excitatory or / and inhibitory synaptic transmission efficiency. Furthermore, the results are carried out to improve cognitive dificit of children with intrauterine growth restriction. The present research results can be used to guide the clinical treatment and drug development in improving cognitive dificit of children with intrauterine growth restriction.

突触稳态可塑性是近年来提出的一种维持神经回路稳定性的重要机制。在神经网络活动中, 兴奋性和抑制性突触传递通过稳态模式调节其动力学特征，使神经回路的活性自动调整到某一范围，以维持中枢的兴奋性。实验证实在宫内生长受限模型中，海马Schaffer侧枝到CA1区通路的场兴奋性突触后电位降低，提示宫内生长受限时海马CA1区神经网络存在着突触稳态可塑性失衡过程。本项目以膜片钳为主要技术手段，在海马CA1区锥体神经元上研究宫内生长受限时突触稳态可塑性的动力学特征及信号转导途径，并结合免疫组织化学染色和钙荧光成像方法探讨CA1区锥体神经元兴奋性和抑制性受体的表达及细胞内钙浓度变化的规律。研究宫内生长受限时海马突触稳态可塑性的变化和机制，以便通过调节兴奋性或/和抑制性突触传递效能，促进神经网络的稳态化，改善宫内生长受限患儿的认知障碍。研究成果可用于指导临床治疗和药物开发等领域。

认知障碍是宫内生长受限( IUGR）新生儿的一个远期并发症。据报道，全球每年出生的新生儿中，5%-10%为IUGR儿，其中25%-34%在儿童期出现认知障碍等神经系统后遗症，表现为学龄期学习成绩差、注意力集中短暂、社会行为能力障碍，部分儿童甚至发生脑瘫。前期大量的研究已经表明，IUGR海马CA1区结构、CA1区锥体神经元代谢及在海马CA1区记录的LTP发生了改变，没有揭示出IUGR认知障碍突触稳态可塑性的动力学特征及机制。本研究揭示了正常组和IUGR大鼠海马NMDA和AMPA受体的亚型变化及它们介导的微小性突触后电流，并进一步探讨了突触后树突棘的形态和密度变化。结果表明，IUGR雄鼠海马CA1 区锥体神经元NMDA 受体介导的微小性兴奋性突触后电流（mEPSC-NMDA)和AMPA 受体介导的的微小性兴奋性突触后电流（mEPSC-AMPA)幅度和频率均减小，其NMDA受体的NR1和NR2B蛋白表达水平降低而NR2A蛋白表达水平升高，而AMPA受体的GluR1、GluR2和GluR3蛋白表达水平均降低，突触后PSD95蛋白和转运NR2B的KIF17蛋白均表达降低，锥体神经元树突棘密度降低，其中主要是蘑菇形树突棘减少明显。IUGR组雌鼠海马微小性兴奋性突触后电流幅度和频率也均减小，而NMDA受体的NR1蛋白和突触后PSD95蛋白表达水平无明显变化。以上结果表明，宫内生长受限认知障碍的发生与海马突触后NMDA和AMPA受体的亚型变化关系密切，而且具有性别差异性。未来可能通过直接调节NMDA和AMPA受体的表达或间接调控KIF17和PSD95蛋白等的表达改善宫内生长受限海马突触稳态可塑性的变化，促进神经网络兴奋性突触传递效能，改善宫内生长受限患儿的认知障碍。研究成果可用于指导临床治疗和药物开发等领域。