Operant Conditioning of Spinal Reflexes to Improve Function after Nerve Injury

描述(由申请人提供)： 每年有数十万美国人受到周围神经损伤的影响，其中包括许多退伍军人。尽管受损的神经可以再生并重新支配周围靶点，但完全恢复正常的运动功能是不寻常的。绝大多数人都患有永久性的运动缺陷。脊髓中不适当的感觉运动连接导致了这些缺陷：支持运动等运动功能的脊髓反射电路紊乱。例如，在周围神经和再生后，IA组来自肌梭的初级传入不再强烈地兴奋同名和协同肌肉的脊髓运动神经元。一种新的治疗方法，能够指导脊髓内适当的感觉运动连接的恢复，可以促进周围神经损伤后的功能恢复和再生。在过去的30年里，我们开发并应用了一种独特的操作条件方案来诱导活性依赖的中枢神经系统可塑性，探索其机制，并将其用于治疗。这个方案在大脑的下行通路中诱导活动，可以修改特定的脊椎反射通路，例如H反射的全脊髓和主要单突触通路，即脊柱伸展反射的电模拟(即膝跳反射)。对于患有不完全脊髓损伤、运动能力受损的动物或人，适当的反射调节方案可以恢复更多的正常运动。此外，最近的初步数据表明，反射训练也可以改善坐骨神经切断和再生后的大鼠的运动能力。基于这项工作，我们假设，适当的反射操作性条件反射方案可以改善周围神经损伤和再生后的运动能力。为了验证这一假设，我们将横断大鼠的右侧坐骨神经，修复(即重新对抗)神经以使再生发生，并评估上调(即增加)或下调(即减少)右侧比目鱼肌H反射的影响。在目标1中，我们将确定在坐骨神经再生期间，上下调节比目鱼肌H反射对运动的影响。在目标2中，我们将确定在坐骨神经再生已经发生后，上调或下调比目鱼肌H反射对运动的影响。每个目标将研究三组大鼠：上条件组、下条件组和对照组(即，简单地测量H反射)。我们将从生理学(即自发的肌电活动、H反射)、功能(即跑步机运动时的肌电和运动学)和免疫组织化学(即比目鱼肌运动神经元上假定的初级传入终末(即含有囊泡性谷氨酸转运体1(VGLUT1)的终末))来评估这些群体。在每个目标的数据收集结束时，我们预计上状态大鼠的比目鱼肌H反射将比对照组或下状态大鼠更大，运动能力将更好(例如，更长的步数，更好的左右对称性，在计时和髋部高度上)。此外，我们预计VGLUT1(即可能的初级传入终末)在高状态大鼠的比目鱼肌运动神经元上将更多和/或更大。因此，这项建议试图评估一种新的、临床实用的治疗方法，以减少与周围神经损伤和再生相关的功能损害。如果这项工作取得成功，将验证反射操作式训练作为一种新的方法，可以补充标准的康复方案，促进周围神经损伤和再生后有用功能的恢复，并为这一新疗法的临床推广铺平道路。

DESCRIPTION (provided by applicant): Peripheral nerve injuries affect hundreds of thousands of Americans every year, including many Veterans. Even though injured nerves can regenerate and reinnervate peripheral targets, complete recovery of normal motor function is unusual. A large majority are left with permanent motor deficits. Inappropriate sensorimotor connections in the spinal cord contribute to these deficits: the spinal reflex circuits that support motor functions such as locomotion are disordered. For example, after peripheral nerve and regeneration, Group IA primary afferent input from muscle spindles no longer strongly excites the spinal motoneurons of homonymous and synergist muscles. A new therapeutic method that can guide the restoration of appropriate sensorimotor connections in the spinal cord could improve functional recovery after peripheral nerve injury and regeneration. Over the past 30 years, we have developed and applied a unique operant conditioning protocol for inducing activity-dependent CNS plasticity, exploring its mechanisms, and using it therapeutically. This protocol induces activity in descending pathways from the brain that can modify specific spinal reflex pathways, such as the wholly spinal and largely monosynaptic pathway of the H-reflex, the electrical analog of the spinal stretch reflex (i.e., the knee-jerk reflex). In animals or people with incomplete spinal cord injuries that have impaired locomotion, an appropriate reflex conditioning protocol can restore more normal locomotion. Furthermore, recent preliminary data suggest that reflex conditioning can also improve locomotion in rats that have undergone sciatic nerve transection and regeneration. Based on this work, we hypothesize that an appropriate reflex operant conditioning protocol can improve locomotion after peripheral nerve injury and regeneration. To test this hypothesis, we will transect the right sciatic nerve in rats, repair (i.e., reoppose) the nerve so that regeneratin occurs, and assess the impact of up-conditioning (i.e., increasing) or down-conditioning (i.e, decreasing) the right soleus H-reflex. In Aim 1, we will determine the locomotor impact of up- or down-conditioning the soleus H-reflex during the period of sciatic regeneration. In Aim 2, we will determine the locomotor impact of up- or down-conditioning the soleus H-reflex after sciatic regeneration has already occurred. Each aim will study three rat groups: up-conditioned; down-conditioning; and control (i.e., the H-reflex is simply measured). We will assess these groups physiologically (i.e., spontaneous EMG activity, H-reflexes), functionally (i.e., EMG and kinematics during treadmill locomotion), and immunohistochemically (i.e., putative primary afferent terminals (i.e., terminals containing vesicular glutamate transporter-1 (VGLUT1)) on soleus motoneurons). At the end of data collection for each aim, we expect that the soleus H-reflex will be larger and locomotion will be better (e.g., longer steps, better right/left symmetryin timing and hip heights) in up- conditioned rats than in control rats or down-conditioned rats. Furthermore, we expect that VGLUT1 (i.e., putative primary afferent terminals) will be more numerous and/or larger on soleus motoneurons of up- conditioned rats. Thus, this proposal seeks to evaluate a novel and clinically practical therapeutic approach to reducing the functional impairments associated with peripheral nerve injury and regeneration. If this work is successful, it will validate reflex operant conditioning as a new method that can compliment standard rehabilitation regimens and enhance the recovery of useful function after peripheral nerve injury and regeneration; and it will prepare the way for clinical translation of this novel therapy.