Sciatic ligation, spinal plasticity and neuropathic pain

描述(申请人提供)：脊髓背角的活动依赖性可塑性可能至少部分是周围神经损伤后神经病理性疼痛发展的基础。这种形式的可塑性可以增强神经元的交流，在大脑中，它可能会使学习和记忆成为可能。然而，在脊髓背角，它可能会将基本的、但迅速终止的急性疼痛感觉转变为非生产性的持续性疼痛。在这一应用中，我们建议采用已建立的神经病理性疼痛的坐骨神经松散结扎模型，并研究在损伤诱导的脊髓可塑性的早期阶段，即坐骨神经结扎后的最初几个小时，脑源性神经营养因子(BDNF)和氯化钾共转运体2(KCC2)之间的潜在相互作用。我们的中心假设是，BDNF介导的KCC2下调促进了背角神经元兴奋性的早期增加。我们推测，这种兴奋性的增加对脊髓可塑性的最初发展以及随后出现的神经病理性疼痛的早期行为迹象有重要贡献。在具体目标1中，我们将研究坐骨神经结扎对背角KCC2基因表达和蛋白水平的早期影响，并确定KCC2水平的变化是否依赖于高亲和力BDNF TrkB受体的激活。在特定的目标2中，我们将从功能上评估坐骨神经结扎或局部应用BDNF对神经元兴奋性的早期影响，并确定TrkB受体或KCC2活性是否改变这种兴奋性。在具体目标3中，我们将建立TrkB受体或KCC2活性的药理操作与神经病理性疼痛早期表达的行为学相关性。神经病理性疼痛是一个严重的健康问题，对生活质量有深远的影响。这是一种使人虚弱的疾病，影响着数百万人，并造成数十亿美元的医疗保健成本和生产力损失。通过详细研究BDNF和KCC2之间的相互作用，我们希望实现两个目标。首先，从纯生物学的角度，我们希望描绘周围神经损伤对背角神经元活动的早期影响。其次，从治疗的角度来看，我们寻求为未来更有效的治疗干预实现更好的靶向性。

DESCRIPTION (provided by applicant): Activity-dependent plasticity in the spinal dorsal horn may at least partly underlie the development of neuropathic pain following peripheral nerve injury. This form of plasticity allows for enhanced neuronal communication, and in the brain, it may enable learning and memory. However, in the spinal dorsal horn it may transform the essential but rapidly terminated sensation of acute pain into unproductive persistent pain. In this application we propose to employ the well-established loose ligation of the sciatic nerve model of neuropathic pain, and investigate the potential interaction between brain derived neurotrophic factor (BDNF) and the potassium-chloride co-transporter 2 (KCC2) in the early phase of injury-elicited spinal plasticity, i.e., in the first few hours after sciatic ligation. Our central hypothesis is that BDNF-mediated down-regulation of KCC2 promotes an early increase in dorsal horn neuronal excitability. We surmise that this increase in excitability contributes significantly to the initial development of spinal plasticity and to the ensuing early behavioral signs of neuropathic pain. In Specific Aim 1 we will examine the early consequences of sciatic ligation on KCC2 gene expression and protein levels in the dorsal horn, and establish if changes in KCC2 levels are dependent on the activation of the high-affinity BDNF TrkB receptors. In Specific Aim 2 we will functionally assess the early consequences of sciatic ligation or local BDNF application on neuronal excitability, and we will determine if a block of TrkB receptors or KCC2 activity modifies this excitability. In Specific Aim 3 we will establish the behavioral relevance of the pharmacological manipulation of TrkB receptors or KCC2 activity on the early expression of neuropathic pain. Neuropathic pain is a serious health problem with profound effects on the quality of life. It is a debilitating disease that affects millions of people and costs billions of dollars in health care and lost productivity. Through a detailed examination of the interplay between BDNF and KCC2 we hope to achieve two goals. First, from a purely biological perspective we wish to delineate the early consequences of peripheral nerve injury on dorsal horn neuronal activity. Second, from a therapeutic perspective, we seek to achieve better target specificity for more effective future therapeutic interventions.