Reorganization of a Dopamine-Sensitive Locomotor Neural Network

几乎所有活着的有机体都需要运动才能生存，这种运动通常是有节奏的，并在动物的腿、翅膀、鳍或其他身体部位高度协调。这种协调是如何协调的还不是很清楚，但失去对运动至关重要的神经细胞的后果是显而易见的，例如，在脊髓损伤期间。这个项目研究神经系统如何在受到重大干扰或损伤后重新调节，以恢复其以前产生有节奏的运动模式的能力。这种重组解决了神经科学中一个新出现的和非常重要的问题--理解体内平衡可塑性的细胞机制。从本质上讲，这种可塑性使系统能够在扰动后返回到其设定点或恢复其原始运行状态。目前，对运动相关的动态平衡机制知之甚少。为了了解这些事件，在单个神经元的水平上，这个项目将使用细胞、分子和行为方法相结合的方法来研究正在恢复的神经系统如何实现转化。科学团队选择将药用水蚤作为运动控制和稳态可塑性的模型进行研究，因为它具有实验可及性和研究良好的运动电路。它用于爬行行为的中央模式生成器(CPG)已被证明受多巴胺的调节，多巴胺是大多数动物中普遍存在的运动活动调节器；每个CPG都位于组成神经索的每个节段性神经节中。该项目引人注目的方面是发现爬行CPG如何重新调整或重新配置，以便在不重新连接头部输入的情况下完全恢复所有计时事件。将检验三个假说：1)来自体壁的本体感觉输入替代脑特定的计时事件；2)紧靠神经索损伤部位下方的神经节中的CPG带头启动和引导尾部方向的亚时爬行波；3)CPG导联基因表达模式的变化为DA和/或本体感觉输入提供了较低的爬行激活阈值。实验方法包括电生理学、免疫细胞化学、共聚焦成像、行为视频捕获、计算神经科学和尖端单细胞定量聚合酶链式反应。该项目的成果有可能影响生物科学以外的不同领域，包括物理、数学、计算机科学和工程学。计划中的水蛭转录组的开发也将推动药用水蛭模型进入基因组学时代。该项目将支持对女性和少数群体参与者的培训、几个以水蛭为基础的实验室教学模块，以及使用面向中学生的水蛭Critter-Cam的社区推广项目。

Almost all living organisms need to move for their survival, and that locomotion is often rhythmic and highly coordinated across an animal's legs, wings, fins, or other body parts. How such coordination is orchestrated is not well understood, but the consequences of losing nerve cells that are vital for locomotion, for example, during a spinal cord injury, are strikingly clear. This project examines how the nervous system can be retuned after a significant perturbation or injury to regain its former ability to generate rhythmic patterns of locomotion. Such reorganization addresses an emerging and highly significant problem in the neurosciences -that of understanding the cellular mechanisms of homeostatic plasticity. Essentially, this plasticity enables a system to go back to its set point or regain its original operational status after a perturbation. Currently, very little is known about locomotor-related homeostatic mechanisms. To understand such events, at the level of individual neurons, this project will use a combination of cellular, molecular and behavioral methods to study how a recovering nervous system achieves its transformation. The scientific team has chosen to study the medicinal leech as a model of locomotor control and homeostatic plasticity because of its experimental accessibility and well-studied locomotor circuits. Its central pattern generators (CPGs) for crawling behavior have been shown to be regulated by dopamine, a universal modulator of motor activity in most animals; each of these CPGs is located within each and every segmental ganglion comprising the nerve cord. The compelling aspect of this project is discovering how the crawl CPGs become retuned or reconfigured so that all timing events are fully restored without the physical reconnection of cephalic inputs. Three hypotheses will be tested: 1) proprioceptive inputs from the body wall substitute for brain-specific timing events; 2) the CPG in the ganglion immediately below the site of nerve cord injury takes the lead in initiating and directing the metachronal crawl waves in the caudal direction; 3) changes in gene expression patterns in the lead CPG provide for a lower crawl-activation threshold to DA and/or proprioceptive inputs. Experimental methods will include electrophysiology, immunocytochemistry, confocal imaging, behavioral video-capture, computational neuroscience, and cutting-edge single-cell quantitative PCR. This project's outcomes have potential to impact disparate fields outside of the biological sciences, including physics, math, computer science and engineering. The planned development of a leech transcriptome will also propel the medicinal leech model into the era of genomics. The project will support the training of female and minority participants, several leech-based laboratory teaching modules, and community outreach projects involving a leech Critter-Cam for middle school students.