应激相关的突触可塑性

下丘脑室旁核小细胞广泛接受谷氨酸能(glutamatergic)和γ-氨基丁酸能(GABAergic)神经终末,并在其胞体形成突触连接。应激可以影响这些突触连接并改变其可塑性,而导致下丘脑-垂体-肾上腺轴(HPA轴)的应激反应能力发生变化。     

大脑皮层I型mGluRs参与突触可塑性调控的机制

<正>I型代谢型谷氨酸受体(metabotropic glutamate receptors,mGluRs)在中枢神经系统(central nervou sysytem,CNS)中参与了很多重要的生理功能,如调控兴奋性神经信号传导,参与痛觉、痒、以及药物成瘾的产生,并且与癫痫、脑缺血、帕金森病等神经系统疾病有密切联系~[1]。然而,以I型mGluRs为药物靶点的药物并不广泛,主要是其作用的机制并不清楚。而研究mGluR1/5在神经系统中发挥功能的作用机制,     

钙调蛋白激酶Ⅱ的结构及其在神经系统中的作用

钙离子（Ca²⁺ ）是通过局部信号获得特异性刺激的关键细胞内信使分子。Ca²⁺ 结合蛋白,如钙调蛋白（CaM）及其靶蛋白是Ca²⁺ 依赖性反应信号传导的关键靶点。钙/钙调蛋白依赖性蛋白酶Ⅱ（CaMKⅡ）是一种多聚体酶,它是哺乳动物前脑总蛋白的重要组成部分,并且是形成突触后致密部的主要成分。近年来国内外研究显示,CaMKⅡ包含α、β、γ 和 δ 4种亚型,其中α 和 β 主要在神经组织中表达,而 γ 和 δ 则在全身多种组织均有表达,它们参与特定的突触可塑性和记忆巩固过程,对神经系统的兴奋性及一些神经系统疾病的发生起重要作用。前期也有研究表明CaMKⅡδ在促进神经元存活中起重要作用。本文就CaMKⅡ的结构及其在神经系统中的作用和与相关神经系统疾病的关系作一综述。     

海马突触可塑性与神经系统相关疾病关系的研究进展

海马突触可塑性直接影响着海马功能的形成和运转过程,尤其是学习和记忆能力的建立和维持。海马突触可塑性与阿尔茨海默病(AD)抑郁症、癫痫等的发生发展存在密切关系。突触可塑性涉及多个方面,不同疾病的突触可塑性改变也不尽相同,因此,它与疾病之间的因果关系以及机制至今尚不十分明确,其影响因素也是多样的。人们已经注意到细胞移植、富集环境(EE)和体育锻炼等直接或间接影响着突触可塑性。从突触可塑性入手寻找有效治疗手段,为神经系统相关疾病防治提供新的思路。因此,改善海马突触可塑性逐渐成为神经系统相关疾病防治的重要策略。本文从海马突触可塑性相关的疾病及影响因素两个方面阐述突触可塑性的研究进展。     

神经细胞粘附分子与老年性痴呆突触可塑性研究进展

目的:神经细胞粘附分子(NCAM)是细胞粘附分子中的一种,它介导细胞间的粘附,既有许多有益的生物学作用,又与许多疾病的发生发展有关。近来研究表明,NCAM与老年性痴呆的神经元突触可塑性关系密切,参与了其学习记忆过程。本文将概述NCAM的结构和功能及其与老年性痴呆突触可塑性的研究进展。     

脊髓背角长时程增强中CaMKⅡ磷酸化水平的变化

目的探讨长时程增强诱导和维持过程中脊髓背角钙/钙调蛋白依赖性蛋白激酶Ⅱ(CaMKⅡ)磷酸化水平的变化。方法(1)细胞外记录脊髓腰膨大部背角浅层神经元C-纤维诱发电位;(2)免疫组化技术观察脊髓背角CaMKⅡ磷酸化水平的变化。结果(1)LTP30min、LTP3h脊髓背角CaMKⅡThr286的磷酸化水平明显高于对照组;(2)强直刺激前30min脊髓局部给予KN-93(CaMKⅡ选择性抑制剂,100μmol/L),LTP的诱导被完全阻断,CaMKⅡ磷酸化水平与对照组无明显差别;(3)强直刺激后30min给予KN-93,明显抑制LTP,CaMKⅡ的磷酸化水平也显著降低;(4)LTP3h后给予KN-93,LTP幅度和CaMKⅡ磷酸化水平与用药前相比,差异没有统计学意义。结论CaMKⅡ磷酸化可能在脊髓背角C-纤维诱发电位长时程增强诱导和早期维持中发挥重要作用。     

钙/钙调蛋白依赖性蛋白激酶Ⅱ在大鼠生后海马发育中的表达

目的 探讨Wistar大鼠生后海马发育过程中钙/钙调蛋白依赖性蛋白激酶Ⅱ（CaMKⅡ）的表达。 方法 应用免疫荧光方法检测CaMKⅡ在生后不同时期大鼠海马CA1、CA3区和齿状回（DG）中的表达情况（n =48）。结果 CaMKⅡ于生后各期海马CA1区和DG的表达逐渐增强,生后第10天（P10）达高峰期,此后逐渐减弱;于CA3区的表达在P4和P10时均较高。其中,CaMKⅡ在CA3区的表达高于在CA1区和DG的表达,在多形层和分子层的表达高于在锥体细胞层或颗粒细胞层的表达。结论 CaMKⅡ在CA1、CA3区和DG中的表达具有特异性的时空分布模式,这可能与其在生后发育过程中的突触发生,树突、轴突形成,海马的成熟以及学习记忆功能相关。     

Cofilin表达调控与神经突触可塑性研究进展

正肌动蛋白(actin)是真核细胞中最丰富的蛋白质,参与诸多重要生理活动,切丝蛋白(cofilin)作为一种Actin结合蛋白,对于维持Actin的动态变化和由Actin参与的各种生理或病理过程具有重要的调控作用。近年来,Cofilin及其相关调控与神经系统损伤或疾病、学习记忆高级脑功能等的关系研究也在日益深入,而这些神经科学问题很多又与神经突触可塑性机制密切相关。     

戊四氮急性癫痫模型齿状回分子层突触的可塑性变化

目的：探讨戊四氮(pentetrazole,PTZ)急性癫痫模型大鼠齿状回分子层突触的可塑性变化。方法：采用PTZ诱发大鼠急性癫痫发作,采用透射电镜观察,对癫痫大鼠海马齿状回分子层内突触的密度、不同形式突触连接面的数量变化进行了研究。结果：(1)PTZ后3d,大鼠海马齿状回分子层内突触密度明显下降,PTZ后7d、14d,突触密度则恢复到与对照组相似的水平。(2)与对照组及PTZ后3d相比,PTZ后7d,笑型突触占突触总数比例明显减少,愁型突触所占比例明显增加。结论：癫痫敏感性长期增强是癫痫长期反复发作的原因之一,而癫痫敏感性增强的时间出现于急性癫痫发作后7d左右。     

Expression of calcium/calmodulin-dependent protein kinase Ⅱ in the hippocampal subregions of the rat during postnatal development

目的 探讨Wistar大鼠生后海马发育过程中钙/钙调蛋白依赖性蛋白激酶Ⅱ(CaMKⅡ)的表达.方法 应用免疫荧光方法检测CaMKⅡ在生后不同时期大鼠海马CA1、CA3区和齿状回(DG)中的表达情况(n=48). 结果 CaMKⅡ于生后各期海马CA1区和DG的表达逐渐增强,生后第10天(P10)达高峰期,此后逐渐减弱;于CA3区的表达在P4和P10时均较高.其中,CaMKⅡ在CA3区的表达高于在CA1区和DG的表达,在多形层和分子层的表达高于在锥体细胞层或颗粒细胞层的表达. 结论 CaMKⅡ在CA1、CA3区和DG中的表达具有特异性的时空分布模式,这可能与其在生后发育过程中的突触发生,树突、轴突形成,海马的成熟以及学习记忆功能相关.     

Surface trafficking of N-methyl-D-aspartate receptors: physiological and pathological perspectives

The N-methyl-D-aspartate receptor (NMDAR) plays a crucial role in shaping the strength of synaptic connections. Over the last decades, extensive studies have defined the cellular and molecular mechanisms by which synaptic NMDARs control the maturation and plasticity of synaptic transmission, and how altered synaptic NMDAR signaling is implicated in neurodegenerative and psychiatric disorders. It is now clear that activation of synaptic or extrasynaptic NMDARs produces different signaling cascades and thus neuronal functions. Our current understanding of NMDAR surface distribution and trafficking is only emerging. Exchange of NMDARs between synaptic and extrasynaptic areas through surface diffusion is a highly dynamic and regulated process. The aim of this review is to describe the identified mechanisms that regulate surface NMDAR behaviors and discuss the impact of this new trafficking pathway on the well-established NMDAR-dependent physiological and pathophysiological processes.     

Synaptic plasticity in the subiculum

The subiculum is the principal target of CA1 pyramidal cells. It functions as a mediator of hippocampal–cortical interaction and has been proposed to play an important role in the encoding and retrieval of long-term memory. The cellular mechanisms of memory formation are thought to include long-term potentiation (LTP) and depression (LTD) of synaptic strength. This review summarizes the contemporary knowledge of LTP and LTD at CA1–subiculum synapses. The observation that the underlying mechanisms of LTP and LTD at CA1–subiculum synapses correlate with the discharge properties of subicular pyramidal cell reveals a novel and intriguing mechanism of cell-specific consolidation of hippocampal output.     

吗啡依赖戒断焦虑大鼠海马突触结构的可塑性

目的:通过对吗啡依赖戒断后焦虑模型大鼠海马突触形态结构可塑性的观察,探讨其焦虑情绪的发生机制。方法:采用剂量递增法建立大鼠吗啡依赖戒断后焦虑模型。取海马CA1、CA3区组织进行透射电镜观察和体视学定量分析。结果:焦虑模型组大鼠海马CA1、CA3区均可见突触密集、数量多,但体积比较小。CA1区突触数密度、面密度均较对照组显著增高,而突触连接带平均面积显著减小;CA3区突触数密度、面密度较对照组同样明显增高,而突触连接带平均面积明显减小。结论:突触形态结构的可塑性变化可能参与了吗啡依赖戒断后焦虑情绪的发生。     

Synaptic receptor trafficking: the lateral point of view

Activity dependent modification of receptors in the post-synaptic density is a key determinant in regulating the strength of synaptic transmission during development and plasticity. A major mechanism for this recruitment and removal of postsynaptic proteins is the lateral diffusion in the plane of the plasma membrane. Therefore, the processes that regulate this lateral mobility are of fundamental importance. In recent years significant progress has been achieved using optical approaches such as single particle tracking (SPT) and fluorescence recovery after photobleach (FRAP). Here, we provide an overview of the principles and methodology of these techniques and highlight the contributions they have made to current understanding of protein mobility in the plasma membrane.     

吗啡依赖戒断焦虑大鼠杏仁核突触结构的可塑性

目的通过对吗啡依赖戒断焦虑模型大鼠杏仁核突触形态结构可塑性的观察,探讨其焦虑情绪发生的机制。方法采用剂量递增法建立大鼠吗啡依赖戒断后焦虑模型。取脑杏仁核进行突触的透射电镜观察和体视学定量分析。结果焦虑模型组大鼠杏仁核可见突触密集、数量多,但体积明显减小。与对照组比较,焦虑模型组大鼠杏仁核突触数密度、面密度均显著增高(P<0.01),突触连接带平均面积减小(P<0.05);而与丁螺环酮组比较,焦虑模型组大鼠杏仁核突触数密度、面密度也显著增高(P<0.01),而突触连接带平均面积减小(P<0.05)。结论杏仁核突触形态结构的可塑性变化可能参与了吗啡依赖戒断后焦虑情绪的发生。     

Synaptic microenvironments--structural plasticity, adhesion molecules, proteases and their inhibitors

Proteolytic regulation might be essential in neural plasticity in mature brain as well as the developing brain. An increasing number of studies support the idea that structural changes in the synapses are closely associated with synaptic plasticity. Proteases and their inhibitors in a synaptic microenvironment are important in the regulation of dynamic changes in the extracellular matrix components associated with synaptic plasticity. In the present article, the possible roles of neuronal proteases, protease inhibitors and extracellular macromolecules are reviewed.     

A role for synaptopodin and the spine apparatus in hippocampal synaptic plasticity

Spines are considered sites of synaptic plasticity in the brain and are capable of remodeling their shape and size. A molecule that has been implicated in spine plasticity is the actin-associated protein synaptopodin. This article will review a series of studies aimed at elucidating the role of synaptopodin in the rodent brain. First, the developmental expression of synaptopodin mRNA and protein were studied; secondly, the subcellular localization of synaptopodin in hippocampal principal neurons was analyzed using confocal microscopy as well as electron microscopy and immunogold labelling; and, finally, the functional role of synaptopodin was investigated using a synaptopodin-deficient mouse. The results of these studies are: (1) synaptopodin expression by hippocampal principal neurons develops during the first postnatal weeks and increases in parallel with the maturation of spines in the hippocampus. (2) Synaptopodin is sorted to the spine compartment, where it is tightly associated with the spine apparatus, an enigmatic organelle believed to be involved in calcium storage or local protein synthesis. (3) Synaptopodin-deficient mice generated by gene targeting are viable but lack the spine apparatus organelle. These mice show deficits in synaptic plasticity as well as impaired learning and memory. Taken together, these data implicate synaptopodin and the spine apparatus in the regulation of synaptic plasticity in the hippocampus. Future studies will be aimed at finding the molecular link between synaptopodin, the spine apparatus organelle, and synaptic plasticity.     

Regulation of AMPA receptors and synaptic plasticity

Neuronal activity controls the strength of excitatory synapses by mechanisms that include changes in the postsynaptic responses mediated by AMPA receptors. These receptors account for most fast responses at excitatory synapses of the CNS, and their activity is regulated by various signaling pathways which control the electrophysiological properties of AMPA receptors and their interaction with numerous intracellular regulatory proteins. AMPA receptor phosphorylation/dephosphorylation and interaction with other proteins control their recycling and localization to defined postsynaptic sites, thereby regulating the strength of the synapse. This review focuses on recent advances in the understanding of the molecular mechanisms of regulation of AMPA receptors, and the implications in synaptic plasticity.     

Inner hair cell ribbon synapse plasticity might be molecular basis of temporary hearing threshold shifts in mice

Recent studies have reported that noise exposure at relatively low intensities can cause temporary threshold shifts (TTS) in hearing. However, the mechanism underlying the TTS is still on debate. Here, we report that an acoustic stimulation (100 dB SPL, white noise) induced TTS in mice, with the maximal ABR threshold elevations seen on the 4^th day after noise exposure. On the other hand, there were no significant morphological changes in the cochlea. Further, there were paralleled changes of pre-synaptic ribbons in both the number and postsynaptic density (PSDs) during this noise exposure. The numbers of presynaptic ribbon, postsynaptic density (PSDs), and colocalized puncta correlated with the shifts of ABR thresholds. Moreover, a complete recovery of ABR thresholds and synaptic puncta was seen on the 14^th day after the noise stimulations. Thus, our study may indicate that noise exposure can cause a decline in cochlear ribbon synapses and result in consequent hearing loss. The reduction of synaptic puncta appears reversible and may contribute to hearing restoration in mice after noise exposure.