兴奋抑制平衡对神经环路可塑性及行为学的研究

It is hypothesized that balance of excitation to inhibition (E/I balance) regulates the activity of neural circuit and the synaptic output， which are important to the social behavior. However, there is insufficient experimental evidence to support this hypothesis. Clinically, we have yet to find an effective treatment to improve the social interaction ability of these patients. Despite of the differences in genetic causes, Schizophrenia and Autism spectrum disorders share similar psychological symptoms, such as the deficit in social interaction. We took advantage of Xenopus system, which is transparent, to test the neural circuit function from molecular, cellular to behavior level. Our previous research demonstrated that decrease of GABAA receptor-mediated synaptic transmission enlarges dendritic arbor structure, increases spontaneous activity, enlarges spatial-temporal receptive field, decreases temporal precision and affects visually-guided avoidance behavior in Xenopus Laevis. Our results show that expression of a peptide (ICL) corresponding to γ2 subunit of GABAA receptors, inhibit GABAergic synaptic transmission without inducing seizure-like activity by antagonists. Glutamatergic synaptic transmission can be decreased by GluR1ct or GluR2ct in a cell-autonomous manner. However, it remains unknown what moleculars and signaling pathways are involved in the visual information processing and avoidance behavior following the imbalance of excitation to inhibition. Furthermore, it is important to understand how to rescue the deficit in avoidance behavior caused by imbalance of excitation to inhibition by interfering of GABAergic or glutamatergic synaptic transmission. We propose to apply electrophysiology and proteomics to elucidate the mechanism underlying the role of E/I balance in neural circuit information processing and visually-guided avoidance behavior. We will combine the method of CLICK-IT Chemistry and Mass spectrometry to screen for the proteins that are involved in experience-dependent synaptic plasticity and avoidance behavior in vivo. In particular, this project will focus on two important moleculars, calcium/calmodulin-dependent protein kinase II (CaMKII) and cytosolic polyadenylation element binding protein CPEB1. We will test the role of these two moleculars in experience-dependent improvement of avoidance behavior and the electrophysiological effects on neural circuit plasticity. We will try to understand the signaling pathways related to these two signaling moleculars and demonstrate the mechanism of their fundamental interactions. This project will provide a clue for the treatment of Schizophrenia and Autism spectrum disorders.

兴奋抑制平衡对中枢神经系统的信息处理和行为表现起着重要的调控作用。我们的前期研究中发现，短肽（ICL）部分阻断GABAA受体的突触输入后，影响了爪蟾视顶盖神经元树突发育、动作电位发放、时间精度、时空感受野和视觉逃避指数。但是，兴奋抑制平衡调控的下游靶分子却不是很清楚。我们的初步研究结果发现，爪蟾的行为可塑性伴随视顶盖新合成蛋白的变化。我们推测，兴奋抑制平衡的改变可能调节新合成蛋白的产生。本项目拟采用细胞生物学、电生理学和蛋白组等技术，通过改变兴奋或抑制水平，从分子、环路和行为三个层次，筛选行为可塑性依赖的新合成蛋白，并研究其表达变化对神经元功能和行为可塑性的影响。本课题将重点研究钙调蛋白激酶（CaMKII）和细胞质聚腺苷酸化元件结合蛋白（CPEB1）在视觉中枢信息处理和可塑性调节中的机制，为精神分裂症和自闭症等与兴奋抑制平衡相关的疾病机制研究提供新的思路。

大脑神经环路要完成正常的生长发育和功能，必需要在一个稳定的内环境下进行。兴奋抑制平衡对中枢神经系统的信息处理起着重要的调控作用，一些神经系统疾病，如精神分裂症和自闭症，具有相同的兴奋抑制平衡失调现象，但是哪些分子信号通路参与了视觉中枢的信息处理、可塑性调节以及行为的影响并不十分清楚。.本项目使用非洲爪蟾作为模式动物，自行设计并搭建了爪蟾行为学测定装置，优化了视觉刺激条件，证明了爪蟾的视觉逃避行为具有可塑性。使用对二甲苯验证了行为学测试参数和科学统计方法，完善和扩展了行为学研究的动物模型。通过改变视顶盖大脑经验依赖的可塑性变化，利用点击化学（Click-IT chemistry）和质谱测序联用技术，筛选出了一批参与经验依赖的新合成蛋白组份，利用蛋白电泳技术证实了几种新合成蛋白是受经验依赖调控的，包括组蛋白去乙化酶（HDAC3）和β-链蛋白(β-catenin)等。研究了这些新合成蛋白成份在神经环路构建和行为可塑性过程中的作用及机制。我们重点研究了组蛋白去乙化酶家族成员：组蛋白去乙化酶1和3（HDAC1和HDAC3）在兴奋抑制平衡对爪蟾视顶盖神经环路可塑性调节和行为可塑性变化过程中的机制。揭示了兴奋抑制平衡参与了爪蟾的行为可塑性变化调控，阐明了HDAC1和HDAC3参与了视觉经验依赖的神经前体细胞：放射状胶质细胞（Radial glial cells, RGs）的增殖调控。揭示了HDAC1对兴奋性和抑制性突触传递的调节，对神经元结构可塑性和行为可塑性调控的作用和分子机制。迄今为止，本项目在国内外期刊发表8篇论文，其中包括SCI收录5篇，国内核心期刊3篇；国际和国内学术会议12人次。.本项目使用的点击化学和质谱联用技术，为筛选在体新合成蛋白提供了新的解决途径，并很大程度上提高了检测新合成蛋白的灵敏度，具有潜在的应用价值。对前体细胞增殖的机制研究，有助于人们进一步理解放射状胶质细胞在神经发育早期的增殖调节机制和对神经环路构建的重要作用，开拓了HDAC1作用的研究深度，为表面遗传机制研究提供了新的思路。