Janickova Helena, Prado Vania F, Prado Marco A M, El Mestikawy Salah, Bernard Véronique
Department of Physiology and Pharmacology and Department of Anatomy & Cell Biology, Robarts Research Institute, Molecular Medicine Laboratories, The University of Western Ontario, London, Ontario, Canada.
Sorbonne Universités, Université Pierre et Marie Curie UM 119 - CNRS UMR 8246 - INSERM U1130, Neurosciences Paris Seine - Institut de Biologie Paris Seine (NPS - IBPS), Paris, France.
J Neurochem. 2017 Sep;142(6):857-875. doi: 10.1111/jnc.14105. Epub 2017 Jul 11.
Striatal cholinergic interneurons (CIN) are pivotal for the regulation of the striatal network. Acetylcholine (ACh) released by CIN is centrally involved in reward behavior as well as locomotor or cognitive functions. Recently, BAC transgenic mice expressing channelrhodopsin-2 (ChR2) protein under the control of the choline acetyltransferase (ChAT) promoter (ChAT-ChR2) and displaying almost 50 extra copies of the VAChT gene were used to dissect cholinergic circuit connectivity and function using optogenetic approaches. These mice display over-expression of the vesicular acetylcholine transporter (VAChT) and increased cholinergic tone. Consequently, ChAT-ChR2 mice are a valuable model to investigate hypercholinergic phenotypes. Previous experiments established that ChAT-ChR2 mice display an increased sensitivity to amphetamine induced-locomotor activity and stereotypes. In the present report, we analyzed the impact of VAChT over-expression in the striatum of ChAT-ChR2 mice. ChAT-ChR2 mice displayed increased locomotor sensitization in response to low dose of cocaine. In addition, we observed a dramatic remodeling of the morphology of CIN in ChAT-ChR2 transgenic mice. VAChT immunolabeling was markedly enhanced in the soma and terminal of CIN from ChAT-ChR2 mice as previously shown (Crittenden et al. 2014). Interestingly, the number of cholinergic varicosities was markedly reduced (-87%) whereas their size was significantly increased (+177%). Moreover, VAChT over-expression dramatically modified its trafficking along the somatodendritic and axonal arbor. These findings demonstrate that ChAT-ChR2 mice present major alterations of CIN neuronal morphology and increased behavioral sensitization to cocaine, supporting the notion that the increased levels of VAChT observed in these mice make them fundamentally different from wild-type mice.
纹状体胆碱能中间神经元（CIN）对纹状体网络的调节至关重要。CIN释放的乙酰胆碱（ACh）在奖励行为以及运动或认知功能中发挥核心作用。最近，利用在胆碱乙酰转移酶（ChAT）启动子控制下表达通道视紫红质-2（ChR2）蛋白且显示有近50个额外VAChT基因拷贝的BAC转基因小鼠，通过光遗传学方法剖析胆碱能回路的连接性和功能。这些小鼠表现出囊泡乙酰胆碱转运体（VAChT）的过度表达以及胆碱能张力增加。因此，ChAT-ChR2小鼠是研究高胆碱能表型的宝贵模型。先前的实验证实，ChAT-ChR2小鼠对苯丙胺诱导的运动活动和刻板行为表现出更高的敏感性。在本报告中，我们分析了VAChT在ChAT-ChR2小鼠纹状体中过度表达的影响。ChAT-ChR2小鼠对低剂量可卡因表现出运动致敏性增加。此外，我们观察到ChAT-ChR2转基因小鼠中CIN的形态发生了显著重塑。如先前所示（Crittenden等人，2014年），ChAT-ChR2小鼠CIN的胞体和终末中VAChT免疫标记明显增强。有趣的是，胆碱能曲张体的数量显著减少（-87%），而其大小显著增加（+177%）。此外，VAChT的过度表达极大地改变了其沿树突体和轴突分支的运输。这些发现表明，ChAT-ChR2小鼠存在CIN神经元形态的主要改变以及对可卡因行为致敏性增加，支持了在这些小鼠中观察到的VAChT水平升高使其与野生型小鼠有根本差异的观点。
