自由移动小鼠的多通道细胞外记录
Summary
该协议描述了运动皮层（MC）中细胞外记录的方法，以揭示自由移动的有意识小鼠的细胞外电生理特性，以及局部场电位（LFP）和尖峰的数据分析，这对于评估网络神经活动的潜在行为是有用的。
Abstract
该协议旨在通过将电生理信号与自发和/或特定行为相关联来揭示神经元放电和网络局部场电位（LFP）在执行特定任务的行为小鼠中的特性。该技术代表了研究这些行为背后的神经元网络活动的宝贵工具。本文提供了在自由移动的清醒小鼠中进行电极植入和随后的细胞外记录的详细而完整的程序。该研究包括植入微电极阵列的详细方法，使用多通道系统捕获运动皮层 （MC） 中的 LFP 和神经元脉冲信号，以及随后的离线数据分析。在有意识的动物中多通道记录的优点是可以获得和比较更多脉冲神经元和神经元亚型，从而可以评估特定行为与相关电生理信号之间的关系。值得注意的是，本研究中描述的多通道细胞外记录技术和数据分析程序在行为小鼠中进行实验时可以应用于其他大脑区域。
Introduction
局部场电位 （LFP） 是细胞外信号的重要组成部分，反映了大量神经元的突触活动，这些神经元构成了多种行为的神经代码1。神经元活动产生的尖峰被认为有助于 LFP，并且对神经编码很重要2.棘峰和 LFP 的改变已被证明可以介导多种脑部疾病，例如阿尔茨海默病，以及恐惧等情绪3,4。值得注意的是，许多研究都强调，动物清醒和麻醉状态之间的尖峰活性显着不同5.尽管麻醉动物的记录提供了一个机会，可以在高度定义的皮质同步状态下以最小的伪影评估 LFP，但结果在一定程度上与清醒受试者 6,7,8 中的结果不同。因此，使用植入大脑的电极在清醒的大脑状态下检测各种疾病在长时间尺度和大空间尺度上的神经活动更有意义。本手稿为初学者提供了有关如何制作微型驱动系统并使用通用软件设置参数的信息，以快速直接的方式计算尖峰和LFP信号，以便开始记录和分析。
尽管脑功能的非侵入性记录，例如使用脑电图 （EEG） 和从头皮记录的事件相关电位 （ERP），已广泛用于人类和啮齿动物研究，但 EEG 和 ERP 数据的空间和时间特性较低，因此无法检测特定大脑区域内附近树突突触活动产生的精确信号1.目前，通过利用有意识动物的多通道记录，可以通过在多次行为测试中将微驱动系统植入灵长类动物或啮齿动物的大脑中，长期和渐进地记录大脑深层的神经活动 1,2,3,4,5,6,7,8,9 .简而言之，研究人员可以构建一个微型驱动系统，该系统可用于电极或四极管的独立定位，以靶向大脑的不同部位10,11。例如，Chang等人描述了通过组装轻巧紧凑的微型驱动器12来记录小鼠尖峰和LFP的技术。此外，带有定制附件组件的微机械硅探针已上市，用于在行为任务期间记录啮齿动物的多个单个神经元和 LFP13。尽管已经使用了各种设计来组装微型驱动系统，但就整个微型驱动系统的复杂性和重量而言，这些设计仍然取得了有限的成功。例如，Lansink等人展示了一种具有复杂结构的多通道微驱动系统，用于从单个大脑区域14进行记录。Sato等人报道了一种多通道微型驱动系统，该系统具有自动液压定位功能15。这些微型驱动系统的主要缺点是它们太重，老鼠无法自由移动，并且对于初学者来说很难组装。尽管多通道细胞外记录已被证明是一种在行为测试中测量神经活动的合适且有效的技术，但对于初学者来说，记录和分析复杂的微驱动系统获得的信号并不容易。鉴于在自由移动的小鼠16,17中很难开始多通道细胞外记录和数据分析的整个操作过程，本文提出了简化的指南，以介绍使用常用组件和设置制作微驱动系统的详细过程;此外，还提供了通用软件中用于快速直接计算尖峰和LFP信号的参数。此外，在该协议中，由于使用了氦气球，鼠标可以自由移动，这有助于抵消头部和微型驱动系统的重量。总的来说，在本研究中，我们描述了如何轻松构建微驱动系统并优化记录和数据分析过程。
Protocol
所有小鼠均在商业上获得，并在室温为22-25°C和相对湿度为50%-60%的情况下，在12小时光照/ 12小时黑暗循环（当地时间上午08：00点亮）中维持。小鼠可以获得持续的食物和水供应。所有实验均按照华南师范大学《实验动物护理与使用指南》进行，并经机构动物伦理委员会批准。以3-5月龄雄性C57BL/6J小鼠为研究对象。 1.微型驱动系统总成 使用两个支架和一个?…
Representative Results
应用高通（250 Hz）滤波器从原始信号中提取多单元尖峰（图6A）。此外，验证了通过PCA排序的正常小鼠MC的记录单位（图7A-D），并记录了小鼠MC中单位的谷值宽度和波形持续时间。结果表明，小鼠MC推定锥体神经元（Pyn）的谷宽和波形持续时间均高于推定中间神经元（IN）（图7E，F;两个样本Mann-Whitney检验;?…
Discussion
在自由移动的小鼠中，多通道记录被认为是神经科学研究中的一项有用技术，但对于初学者来说，记录和分析信号仍然相当具有挑战性。在本研究中，我们提供了制造微驱动系统和进行电极植入的简化指南，以及 通过 尖峰分选软件和神经生理学数据分析软件捕获和分析电信号的简化程序。
鉴于定制微驱动系统的质量极大地有助于在自由移动的小鼠 14、15<…
Disclosures
The authors have nothing to disclose.
Acknowledgements
这项工作得到了国家自然科学基金（31871170、32170950和31970915）、广东省自然科学基金（2021A1515010804和2023A1515010899）、广东省自然科学基金重大培育项目（2018B030336001）和广东省资助：脑疾病治疗关键技术（2018B030332001）的资助。
Materials
| 2.54 mm pin header | YOUXIN Electronic Co., Ltd. | 1 x 5 | Applying for the movable micro-drive which can slide on its stulls. |
| Adobe Illustrator CC 2017 | Adobe | N/A | To optimize images from GraphPad. |
| BlackRock Microsystems | Blackrock Neurotech | Cerebus | This systems includes headsatge, DA convert, amplifier and computer. |
| Brass nut | Dongguan Gaosi Technology Co., Ltd. | M0.8 brass nut | The nut fixes the position of screw. |
| Brass screw | Dongguan Gaosi Technology Co., Ltd. | M0.8 x 11 mm brass screw | A screw that hold the movable micro-drive. |
| C57BL/6J | Guangdong Zhiyuan Biomedical Technology Co., LTD. | N/A | 12 weeks of age. |
| Centrifuge tube | Biosharp | 15 mL; BS-150-M | To store mice brain with sucrose sulutions. |
| Conducting paint | Structure Probe, Inc. | 7440-22-4 | To improve the lead-connecting quality between connector pins and Ni-wires. |
| Conductive copper foil tape | 3M | 1181 | To reduce interferenc. |
| Connector | YOUXIN Electronic Co., Ltd. | 2 x 10P | To connect the headtage to micro-drive system. |
| DC Power supply | Maisheng | MS-305D | A power device for electrolytic lesion. |
| Dental cement | Shanghai New Century Dental Materials Co., Ltd. | N/A | To fix the electrode arrays on mouse's skull after finishing the implantation. |
| Digital analog converter | Blackrock | 128-Channel | A device that converts digital data into analog signals. |
| Epoxy resin | Alteco | N/A | To cover pins. |
| Excel | Microsoft | N/A | To summarize data after analysis. |
| Eye scissors | JiangXi YuYuan Medical Equipment Co.,Ltd. | N/A | For surgery or cutting the Ni-chrome wire. |
| Fine forceps | JiangXi YuYuan Medical Equipment Co.,Ltd. | N/A | For surgery. |
| Forceps | JiangXi YuYuan Medical Equipment Co.,Ltd. | N/A | For surgery or assembling the mirco-drive system. |
| Freezing microtome | Leica | CM3050 S | Cut the mouse’s brain into slices |
| Fused silica capillary tubing | Zhengzhou INNOSEP Scientific Co., Ltd. | TSP050125 | To serve as the guide tubes for Ni-chrome wires. |
| Glass microelectrode | Sutter Instrument Company | BF100-50-10 | To mark the desired locations for implantation using the filled ink. |
| GraphPad Prism 7 | GraphPad Software | N/A | To analyze and visualize the results. |
| Guide-tube | Polymicro technologies | 1068150020 | To load Ni-chrome wires. |
| Headstage | Blackrock | N/A | A tool of transmitting signals. |
| Helium balloon | Yili Festive products Co., Ltd. | 24 inch | To offset the weight of headstage and micro-drive system. |
| Ink | Sailor Pen Co.,LTD. | 13-2001 | To mark the desired locations for implantation. |
| Iodine tincture | Guangdong Hengjian Pharmaceutical Co., Ltd. | N/A | To disinfect mouse's scalp. |
| Lincomycin in Hydrochloride and Lidocaine hydrochloride gel | Hubei kangzheng pharmaceutical co., ltd. | 10g | A drug used to reduce inflammation. |
| Meloxicam | Vicki Biotechnology Co., Ltd. | 71125-38-7 | To reduce postoperative pain in mice. |
| Micromanipulators | Scientifica | Scientifica IVM Triple | For electrode arrays implantation. |
| Microscope | Nikon | ECLIPSE Ni-E | Capture the images of brain sections |
| nanoZ impedance tester | Plexon | nanoZ | To measure impedance or performing electrode impedance spectroscopy (EIS) for multichannel microelectrode arrays. |
| NeuroExplorer | Plexon | NeuroExplorer | A tool for analyzing the electrophysiological data. |
| NeuroExplorer | Plexon, USA | N/A | A software. |
| Ni-chrome wire | California Fine Wire Co. | M472490 | 35 μm Ni-chrome wire. |
| Offline Sorter | Plexon | Offline Sorter | A tool for sorting the recorded multi-units. |
| PCB board | Hangzhou Jiepei Information Technology Co., Ltd. | N/A | Computer designed board. |
| Pentobarbital | Sigma | P3761 | To anesthetize mice. |
| Pentobarbital sodium | Sigma | 57-33-0 | To anesthetize the mouse. |
| Peristaltic pump | Longer | BT100-1F | A device used for perfusion |
| Polyformaldehyde | Sangon Biotech | A500684-0500 | The main component of fixative solution for fixation of mouse brains |
| PtCl4 | Tianjin Jinbolan Fine Chemical Co., Ltd. | 13454-96-1 | Preparation for gold plating liquid. |
| Saline | Guangdong Hengjian Pharmaceutical Co., Ltd. | N/A | To clean the mouse's skull. |
| Silver wire | Suzhou Xinye Electronics Co., Ltd. | 2 mm diameter | Applying for ground and reference electrodes. |
| Skull drill | RWD Life Science | 78001 | To drill carefully two small holes on mouse's skull. |
| Stainless steel screws | YOUXIN Electronic Co., Ltd. | M0.8 x 2 | To protect the micro-drive system and link the ground and reference electrodes. |
| Stereotaxic apparatus | RWD Life Science | 68513 | To perform the stereotaxic coordinates of bilateral motor cortex. |
| Sucrose | Damao | 57-50-1 | To dehydrate the mouse brains after perfusion. |
| Super glue | Henkel AG & Co. | PSK5C | To fix the guide tube and Ni-chrome wire. |
| Temperature controller | Harvard Apparatus | TCAT-2 | To maintain mouse's rectal temperature at 37°C |
| Tetracycline eye ointment | Guangdong Hengjian Pharmaceutical Co., Ltd. | N/A | To protect the mouse's eyes during surgery. |
| Thread | Rapala | N/A | To link ballon and headstage. |
| Vaseline | Unilever plc | N/A | To cover the gap between electrode arrays and mouse's skull. |
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Cite This Article
Ghouse, M., Li, M., Long, C., Jiang, J. Multichannel Extracellular Recording in Freely Moving Mice. J. Vis. Exp. (195), e65245, doi:10.3791/65245 (2023).