Robotic Training and the Modulation of BDNF Activity in Spinally Transected Rats

描述（由申请人提供）：通过跑步机训练，可以改善完全脊髓横断（ST）动物后肢踏步的恢复。我们对跑步机训练改善行走的机制知之甚少，但我们的研究表明，训练增强了产生行走的腰椎脊髓神经元的可塑性。脑源性神经营养因子（BDNF）是神经营养因子家族的一员，已被证明在中枢神经系统的活动依赖性可塑性中起着至关重要的作用。我们拟研究BDNF在ST大鼠后肢跑步机训练后脊髓活动依赖性可塑性中的作用。我们的总体假设是内源性BDNF通过加强控制行走的神经回路中的突触来提高ST大鼠产生后肢行走的能力。在第一个实验中，我们将首先确定腰椎神经元合成BDNF的程度取决于对ST大鼠施加的跑步机训练量。我们将使用一种机器人装置，与传统的跑步机不同，它可以精确控制在跑步机上行走时后肢的活动量。结合原位杂交和免疫组织化学技术，我们将在1天、4周或12周的跑步机训练后，检测腰椎神经元中BDNF mRNA和蛋白、TrkB （BDNF受体）和可塑性相关分子、突触素I、CREB、CaMKII和NMDA受体亚基的表达。在我们的第二个实验中，我们将使用机器人装置在跑步机训练期间施加一个力，选择性地增强一只后肢伸肌神经元的活动。4周后，我们将比较BDNF mRNA和蛋白的表达，以确定更活跃的神经元是否有更高的BDNF表达。在我们的第三个实验中，我们将使用阻断脊髓BDNF活动的药物来确定跑步机训练的效果是否需要BDNF的作用。因此，在项目结束时，我们将知道腰椎神经元中BDNF合成依赖于后肢活动水平的程度，我们将知道BDNF活动是否对ST大鼠的步态恢复至关重要。这些研究将为跑步机训练改善脊髓损伤后行走的机制提供一些重要的见解。此外，研究结果可能提示以活动为基础的策略在脊髓损伤的神经营养治疗中的作用。

DESCRIPTION (provided by applicant): The recovery of hindlimb stepping in complete spinally transected (ST) animals is improved by treadmill training. Little is known about the mechanisms by which treadmill training improves stepping, but our studies suggest that training enhances plasticity in the neurons of the lumbar spinal cord that generate stepping. Brain derived neurotrophic factor (BDNF) is a member of the neurotrophin family and has been shown to play a crucial role in activity-dependent plasticity in the central nervous system. We propose to study the role of BDNF in activity-dependent plasticity in the spinal cord of ST rats that undergo hindlimb treadmill training. Our overall hypothesis is that endogenously-produced BDNF improves the ability of ST rats to generate hindlimb stepping by strengthening synapses within the neural circuits that control stepping. In the first experiment, we will first determine the extent that BDNF synthesis by lumbar spinal neurons is dependent on the amount of treadmill training imposed on the ST rats. We will use a robotic device that, unlike conventional treadmills, allows precise control over the amount of hindlimb activity during treadmill stepping. Using a combination of in situ hybridization and immunohistochemical techniques, we will then examine the expression of BDNF mRNA and protein, TrkB (the receptor for BDNF) and plasticity-related molecules, synapsin I, CREB, CaMKII and NMDA receptor subunits in lumbar spinal neurons following 1 day, 4 or 12 weeks of treadmill training. In our second experiment, we will selectively enhance the activity of extensor neurons in one hindlimb using the robotic device to apply a force during treadmill training. After 4 weeks, we will compare the expression of BDNF mRNA and protein to determine if the more active neurons have higher BDNF expression. In our third experiment, we will administer drugs that block BDNF activity in the spinal cord to determine if the effects of treadmill training require BDNF action. Thus, at the end of the project, we will know the extent that BDNF synthesis in lumbar spinal neurons is dependent on the levels of hindlimb activity and we will know if BDNF activity is crucial for the recovery of stepping in ST rats. These studies will provide some important insight into the mechanisms by which treadmill training improves stepping after spinal cord injury. In addition, the findings may suggest a role for activity-based strategies in neurotrophin treatments for spinal cord injury.