Exploiting endogenous opioids to selectively modulate accumbal synaptic transmission

项目摘要 为了了解成瘾背后的病理生理学，人们付出了巨大的努力。2017年， 美国估计有1970万人符合物质使用障碍的标准。中断 几个相互关联的大脑区域表现为用于诊断成瘾障碍的行为，其中包括 强迫性吸毒是一个标志性症状强迫行为代表了一种控制力受损的状态 重复的动作或想法可能会对正常的行为功能有害。目前没有 针对成瘾症状的治疗。与强迫行为病理生理学有关的是 在驱动动机性行为的关键中枢节点-这些干扰是 与表达Drd 1的中型多棘投射神经元（MSN）的过度活动特别相关 多巴胺受体（D1-MSN），相对于表达Drd2多巴胺受体（D2-MSN）的那些。MSNs 包括大多数细胞内的核，并加强兴奋性突触输入到 D1-MSN有助于成瘾相关行为。这项建议旨在最终恢复核神经元 通过间接参与选择性降低D1-MSN活性的突触可塑性机制发挥作用。 我们的初步研究抑制血管紧张素转换酶（ACE）的肽酶活性，这是高度 由D1-MSN表达，但不被其他神经元细胞类型或脑区域表达。ACE已被证明可以降解 由D2-MSN释放的内源性阿片肽，称为脑啡肽。初步调查结果显示， ACE抑制阿片样物质介导的D1-MSN功能调节但不抑制D2-MSN功能的机制， 而ACE抑制降低了D1-MSNs上的兴奋性突触输入。因此，我们假设ACE抑制 提高激活兴奋性末端上突触前阿片受体的脑啡肽的内源性水平， 从而选择性地抑制D1-MSN上的突触输入。我们提出了两个目标，1）直接评估 内源性脑啡肽在D1-MSNs活性调节中的作用; 2）探讨其机制 这一现象的基础是ACE抑制。第一个目标是将光遗传学与肽结合起来 定量技术和全细胞膜片钳电生理学直接测量生理 内源性脑啡肽的影响。第二个目标将利用电生理学和遗传操作， 识别由ACE抑制介导的突触变化背后的突触前和突触后元件。这 建议将跨学科技术纳入基础科学机制的交叉点， 翻译应用程序将提供无与伦比的培训潜力，成为一个独立的医生 科学家

PROJECT SUMMARY A tremendous effort has been undertaken to understand the pathophysiology underlying addiction. In 2017, an estimated 19.7 million people within the United States met criteria for Substance Use Disorder. Disruptions in several interconnected brain regions manifest as behaviors used to diagnose addiction disorders, which includes compulsive drug-seeking as a hallmark symptom. Compulsive behaviors represent a state of impaired control over repetitive actions or thoughts that can be deleterious to normal behavioral function. There is currently no treatment that addresses this symptom in addiction. Implicated in compulsive behavior pathophysiology are disruptions in nucleus accumbens, a central node critical in driving motivated behaviors. These disruptions are specifically associated with excessive activity of medium spiny projection neurons (MSNs) that express the Drd1 dopamine receptor (D1-MSNs), relative to those that express the Drd2 dopamine receptor (D2-MSNs). MSNs comprise the majority of cells within the nucleus accumbens, and strengthening of excitatory synaptic input onto D1-MSNs contributes to addiction-related behavior. This proposal aims to ultimately restore nucleus accumbens function by indirectly engaging a mechanism of synaptic plasticity that will selectively reduce D1-MSN activity. Our preliminary studies inhibited the peptidase activity of angiotensin converting enzyme (ACE), which is highly expressed by D1-MSNs but not by other neuronal cell types or brain regions. ACE has been shown to degrade endogenous opioid peptides released by D2-MSNs called enkephalins. Preliminary findings suggest a unique mechanism where ACE constrains opioid-mediated regulation of D1-MSN function but not D2-MSN function, and ACE inhibition decreases excitatory synaptic input onto D1-MSNs. Thus, we hypothesize that ACE inhibition elevates endogenous levels of enkephalins which activate presynaptic opioid receptors on excitatory terminals, thereby depressing synaptic input selectively onto D1-MSNs. We propose two aims that will 1) directly evaluate the contribution of endogenous enkephalins in regulating D1-MSNs activity and 2) investigate the mechanism underlying this phenomenon mediated by ACE inhibition. The first aim will integrate optogenetics with peptide quantification techniques and whole-cell patch clamp electrophysiology to directly measure the physiological impact of endogenous enkephalins. The second aim will utilize electrophysiology and genetic manipulations to identify the pre- and postsynaptic elements that underly synaptic changes mediated by ACE inhibition. This proposal’s incorporation of interdisciplinary techniques at the intersection of basic science mechanisms and translational application will provide unparalleled training potential towards becoming an independent physician scientist.