Impact of SAH on Parenchymal Arterioles and Neurovascular Coupling

脑动脉瘤破裂后蛛网膜下腔出血（SAH）与大量发病率相关 并且现有的治疗选择具有有限的功效。几十年来，传统的观点一直是 血液引起的脑表面大直径动脉的血管痉挛是脑血管病的主要原因。 蛛网膜下腔出血患者的迟发性神经功能障碍。然而，新出现的观点是， 包括脑内微循环功能受损会导致不良结果。迄今为止， 研究已经直接检查了SAH对脑中的实质小动脉（PA）的影响。我们 初步数据表明，从SAH模型大鼠中分离的PA表现出增强的收缩。进一步 其中神经元、星形胶质细胞和PA之间的通信是完整的脑切片的背景（即，完整 神经血管单位），我们提供了新的和令人兴奋的证据表明，SAH导致神经血管耦合的转变 从血管舒张到血管收缩。我们认为，蛛网膜下腔出血引起的增强PA收缩和受损 神经血管偶联是两种不同的现象，它们共同作用，对流向脑血管的血流产生负面影响。 个脑袋我们的首要目标是了解促成这些事件的细胞机制。的 具体目标1的目的是确定增强压力诱导的PA收缩的细胞基础， 并了解这种增强的收缩对血管活性影响的影响 与神经血管耦合有关我们的初步数据表明，SAH，通过一个机制，涉及表皮 生长因子受体（EGFR）活化，引起电压依赖性K* 通道（Kv）通道抑制， 平滑肌（SM）细胞膜电位（VM）去极化和增强的电压依赖性Ca^* 通道（Cav）活性。具体目标2将阐明星形胶质细胞尾足Ca^* 和大电导的作用 蛛网膜下腔出血时神经和足端Ca^* 释放引起的血管收缩中Ca^* 激活的K*（BK）通道活性 动物在这里，我们还将研究蛛网膜下腔出血对神经诱发的大脑皮质血流变化的影响。 in vivo.最先进的技术，包括双光子Ca^* 成像和开放，膜片钳 电生理学，定量实时PCR和激光多普勒血流仪应用于一个层次， 从亚细胞水平到完整脑切片和完整动物的实验方法。 该项目将与项目1（M）密切合作。T.纳尔逊，脑切片成像和神经血管耦合;在 功能性充血的体内测量）和项目2（J.E. Brayden、SM Cav和VM研究）。此外，本发明还 我们在PA SM中的K* 通道研究将补充Brayden博士的瞬时受体电位（TRP）通道 问题研究该项目将与M. Cipolla（项目3），因为这些项目使用两种不同形式的模型 尽管在病因和近端功能影响方面存在差异， 神经血管耦合和认知功能的后果。这项工作将大大增加目前 了解SAH对PA功能和神经血管耦合的作用。这些研究还将 提供了可用于鉴定这些病理的关键介质的指纹， 治疗目标，以帮助最大限度地减少脑动脉瘤破裂的破坏性后果。

Subarachnoid hemorrhage (SAH) following cerebral aneurysm rupture is associated with substantial morbidity and mortality and existing therapeutic options have limited efficacy. For decades, the traditional view has been that blood-induced vasospasm of large diameter arteries on the brain surface is the major underiying cause of delayed neurological deficits in SAH patients. However, the emerging view is that additional factors that may include impaired function of the microcirculation within the brain contribute to poor outcome. To date, few studies have directiy examined the impact of SAH on parenchymal arterioles (PAs) in the brain. Our preliminary data demonstrate that isolated PAs from SAH model rats exhibit enhanced constriction. Further, in the context of brain slices where communication between neurons, astrocytes and PAs is intact (i.e., the intact neurovascular unit), we provide novel and exciting evidence that SAH causes a shift in neurovascular coupling from vasodilation to vasoconstriction. We propose that SAH-induced enhanced PA constriction and impaired neurovascular coupling are two distinct phenomena acting in concert to negatively impact blood flow to the brain. Our overarching objective is to understand the cellular mechanisms contributing to these events. The goal of Specific Aim 1 is to determine the cellular basis of enhanced pressure-induced constriction of PAs from SAH animals and to understand the impact that this enhanced constriction has on vasoactive influences implicated in neurovascular coupling. Our preliminary data suggest SAH, via a mechanism involving epidermal growth factor receptor (EGFR) activation, causes voltage-dependent K* channel (Kv) channel suppression, smooth muscle (SM) cell membrane potential (VM) depolarization and enhanced voltage-dependent Ca^* channel (Cav) activity. Specific Aim 2 will elucidate the role of astrocytic endfoot Ca^* and large-conductance Ca^*-activated K* (BK) channel activity in neurally and endfoot Ca^* uncaging evoked vasoconstriction in SAH animals. Here, we will also examine the effect of SAH on neurally evoked cortical cerebral blood flow changes in vivo. State-of-the-art techniques including two-photon Ca^* imaging and uncaging, patch clamp electrophysiology, quantitative real-time PCR and laser Doppler flowmetry are applied to a hierarchy of experimental approaches that range from the subcellular level to the intact brain slice, and the intact animal. This project will work closely with Project 1 (M. T. Nelson, brain slice imaging and neurovascular coupling; in vivo measurements of functional hyperemia) and Project 2 (J. E. Brayden, SM Cav and VM studies). Further, our K* channel studies in PA SM will complement Dr. Brayden's Transient Receptor Potential (TRP) channel studies. This project will interact with M. Cipolla (Project 3), as these projects use models of two distinct forms of stroke, which despite differences in etiology and proximate functional effects, may have similar consequences for neurovascular coupling and cognitive function. This work will greatiy add to current knowledge regarding the actions of SAH on PA function and neurovascular coupling. These studies will also provide fingerprints useful in identifying key mediators of these pathologies and are likely to identify novel therapeutic targets to help minimize the devastating consequences of cerebral aneurysm rupture.