Spinal Effects of Cortical Stimulation: Mechanisms and Functional Impact

项目摘要/摘要 由于依赖活动的可塑性在中枢神经系统中普遍存在，脑刺激可能对 受刺激区域连接到的区域。这些影响几乎没有受到关注。然而，最近 对皮质在塑造脊髓通路中的长期作用的评价表明，长期的脊髓 大脑皮层刺激的影响可能是巨大的。事实上，大脑皮质的弱电刺激(ECS) 大鼠感觉运动皮质具有持久的脊椎效应。ECS结束三个月后，脊髓中的GABA受体 运动神经元仍然减少，H-Reflex(类似于脊髓伸展Reflex)仍然增加。 这项建议试图在大鼠身上确定ECS是如何产生这些脊髓效应的，并表征 对生理、解剖和分子水平的影响。初步研究支持这样一种假设： 脊髓效应的发生是因为ECS兴奋了与脊髓GABA能突触的皮质脊髓束(CST)神经元 在比目鱼肌运动神经元上突触的中间神经元，这种输入减少了GABA代谢性受体和 从而改变运动神经元的特性，从而增加H-refiflex(并且也影响其他脊髓回路)，以及 这种特殊的fic基因激活是这些效应的基础。两个特定的fic目标验证了这一假设。 fi的第一个目标是确定ECS参数如何影响其对脊髓的影响，并确定fiNe 负责任的下行通路。ECS将通过硬膜外电极给予。通路损害与解剖学 示踪剂将识别关键通路及其脊椎靶点。基于初始数据和其他研究，预期 CST是脊髓运动神经元的基本通路，它通过GABA能中间神经元与脊髓运动神经元相连。 第二个目标是表征ECS对脊髓神经元和环路的短期和长期影响。 在生理、解剖和转录水平上。这些研究将：检查ECS对运动神经元的影响 性质(例如，fi环阈值)和对脊髓ReflEX通路的影响；免疫组织化学探讨ECS对 比目鱼肌中的GABA能和其他(如谷氨酸能)脊髓中间神经元和突触及其受体 其他脊髓运动神经元；使用下一代测序方法(RNA-Seq)识别ECS诱导的变化 在脊髓运动神经元中与神经元变化相关并可能解释其变化的基因表达 特性、脊髓回路功能和免疫组织化学测量。 综上所述，这项建议使用了一个很好的fiNed实验模型来探索皮质对脊髓的影响 刺激。通过描述这种刺激产生的脊髓可塑性的性质和机制， 它应该为大脑皮层刺激的更广泛的影响提供根本的新见解，也应该提供如何 皮质莫迪fi的脊髓在一生中。此外，结果应该指导刺激的发展 进一步探讨这些影响的方案，以及可以诱导良好的可塑性以增强fi的刺激方案 中枢神经系统损伤或疾病后的功能恢复。

Project Summary/Abstract Because activity-dependent plasticity is ubiquitous in the CNS, brain stimulation may have long-term effects on areas to which the stimulated area connects. These effects have received little attention. Nevertheless, recent appreciation of the long-term role of cortex in shaping spinal cord pathways suggests that the long-term spinal effects of cortical stimulation are likely to be substantial. In fact, weak electrical cortical stimulation (ECS) of rat sensorimotor cortex has lasting spinal effects. Three months after ECS ends, GABA receptors in spinal motoneurons remain decreased and the H-reflex (analog of the spinal stretch reflex) remains increased. This proposal seeks to determine in rats how ECS produces these spinal effects and to characterize the effects on physiological, anatomical, and molecular levels. Preliminary studies support the hypothesis that the spinal effects occur because ECS excites corticospinal tract (CST) neurons that synapse on spinal GABAergic interneurons that synapse on soleus motoneurons, that this input reduces GABA metabotropic receptors and thereby modifies motoneuron properties so as to increase the H-reflex (and also affect other spinal circuits), and that specific gene activations underlie these effects. Two specific aims test this hypothesis. The first aim is to determine how ECS parameters affect its impact on the spinal cord and to define the responsible descending pathway. ECS will be given by epidural electrodes. Pathway lesions and anatomical tracers will identify the key pathway and its spinal targets. Based on initial data and other studies, the expectation is that the CST is the essential pathway and that it connects to spinal motoneurons via GABAergic interneurons. The second aim is to characterize the short-term and long-term effects of ECS on spinal neurons and circuits on physiological, anatomical, and transcriptional levels. These studies will: examine ECS impact on motoneuron properties (e.g., firing threshold) and on spinal reflex pathways; explore immunohistochemically ECS impact on GABAergic and other (e.g., glutamatergic) spinal interneurons and synapses and their receptors in soleus and other spinal motoneurons; use next-generation sequencing methods (RNA-Seq) to identify ECS-induced changes in gene expression in spinal motoneurons that correlate with and are likely to account for the changes in neuronal properties, spinal circuit function, and immunohistochemical measures. In summary, this proposal uses a well-defined experimental model to explore the spinal effects of cortical stimulation. By characterizing the nature and mechanisms of the spinal cord plasticity produced by this stimulation, it should provide fundamental new insight into the wider effects of cortical stimulation, and also into how the cortex modifies the spinal cord throughout life. Furthermore, the results should guide development of stimulation protocols to further explore these effects, and stimulation protocols that can induce beneficial plasticity to enhance functional recovery after CNS trauma or disease.