Understanding a specific microcircuit that integrates somatosensory information in the dorsal spinal cord

 描述(由申请人提供)：瘙痒是最常见的皮肤病症状之一，有多种原因。大约17%的人口患有特应性皮炎，多达80%的人口在一生中将经历接触性皮炎。患有慢性瘙痒的患者的生活质量显著下降。尽管需求迫切，但目前还没有针对最严重类型的慢性瘙痒的有效治疗方法。缺乏有效疗法的原因之一是，我们仍然不知道哪些神经元和神经回路介导了瘙痒，以及它们是如何调节的。在这项提案中，我们描述了将开始填补这一知识空白的实验。我们的实验室以前曾显示，缺乏转录因子Bhlhb5的小鼠表现出病理性瘙痒，这是由于背角II层(B5-I神经元)中的抑制性中间神经元的子集丢失所致。此外，我们还发现B5-I神经元包括一个分子上不同的群体，表达神经元型一氧化氮合酶(NNOS)。)。[重要的是，我现在有证据表明，板层I中的一部分投射神经元受到nNOS神经元的强烈抑制。这些发现表明，在Bhlhb5突变小鼠中观察到的病理性瘙痒可能至少部分是由于参与调控瘙痒的投射神经元失去了抑制性nNOS神经元的输入。因此，我们假设nNOS神经元选择性地抑制介导瘙痒的投射神经元的子集。在这里，我打算用行为学、解剖学和电生理学的方法来研究nNOS抑制剂中间神经元如何调节躯体感觉过程。特别是，我将利用药物遗传学在体内选择性地抑制nNOS神经元；我将通过共聚焦显微镜从解剖学的角度定义哪些投射神经元受到nNOS介导的抑制；我将在完整的体外准备中结合光遗传学和膜片钳电生理学，以确定nNOS抑制中间神经元如何影响I层投射神经元的功能。总体而言，这些研究将为了解背侧脊髓中可能参与瘙痒调制的特定微回路提供重要的见解。这些实验是开始了解体感回路以及我们如何利用这些信息来开发更有效的慢性瘙痒治疗方法的基本步骤。]

 DESCRIPTION (provided by applicant): Itch is among the most common dermatological complaints, and has various causes. Approximately 17% of the population suffers from atopic dermatitis, and as much as 80% of the population will experience contact dermatitis in their lifetime. Patients suffering from chronic itch experience significantly decreased quality of life. Despite a pressing need, there are no effective treatments for most severe types of chronic itch. One of the reasons that effective therapies are lacking is that we still do not understand which neurons and neural circuits mediate itch and how they are regulated. In this proposal, we describe experiments that will begin to fill this gap in knowledge. Our lab has previously shown mice lacking the transcription factor Bhlhb5 display pathological itch due to the loss of a subset of inhibitory interneurons in lamina II of the dorsal horn (B5-I neurons). In addition, we have discovered B5-I neurons include a molecularly distinct population that expresses neuronal nitric oxide synthase (nNOS). ). [Importantly, I now have evidence that a subset of projection neurons in lamina I receive strong inhibition from nNOS neurons. These findings suggests that the pathological itch observed in Bhlhb5 mutant mice may be due, at least in part, to the loss of inhibitory nNOS neuron input to projection neurons involved in modulating itch. We therefore we hypothesize that nNOS neurons selectively inhibit the subset of projection neurons that mediate itch. Here I propose to investigate how nNOS inhibitor interneurons modulate somatosensory processing using behavioral, anatomical and electrophysiological approaches. In particular, I will selectively inhibit nNOS neurons in vivo using pharmacogenetics; I will define anatomically the subset of which projection neurons are subject to nNOS- mediated inhibition through confocal microscopy; and I will combine optogenetics and patch-clamp electrophysiology in an intact in vitro preparation to determine how nNOS inhibitory interneurons neurons affect the function of lamina I projection neurons. Overall, these studies will provide important insight into a specific microcircuit in the dorsal spinal cord that may be involved in the modulation of itch. These experiments are a fundamental step in beginning to understand somatosensory circuitry and how we can use this information to develop more effective treatments for chronic pruritus.]