Impact of SAH on Parenchymal Arterioles and Neurovascular Coupling

脑动脉瘤破裂后蛛网膜下腔出血(SAH)与发病率显著相关 死亡率和现有的治疗选择效果有限。几十年来，传统观点一直是 脑表面大直径动脉的血液诱发血管痉挛是导致脑血管痉挛的主要原因 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，其他因素可能会 包括大脑内微循环功能受损会导致不良结局。到目前为止，几乎没有人 研究直接检测了蛛网膜下腔出血对大脑实质小动脉(PA)的影响。我们的 初步数据显示SAH模型大鼠分离的PAS表现出增强的收缩作用。此外，在 脑片的上下文，其中神经元、星形胶质细胞和PA之间的通信是完整的(即，完整的 神经血管单位)，我们提供了新的和令人兴奋的证据，证明SAH导致神经血管偶联的转变。 从血管扩张到血管收缩。我们认为SAH诱导的PA收缩和损伤增强 神经血管耦合是两种不同的现象，它们共同作用，对流向大脑的血流产生负面影响 大脑。我们的首要目标是了解导致这些事件的细胞机制。这个 具体目标1的目的是确定压力诱导的PAS收缩增强的细胞学基础。 SAH动物，并了解这种增强的收缩对血管活性影响的影响 牵涉到神经血管耦合。我们的初步数据表明，SAH是通过一种涉及表皮的机制 生长因子受体(EGFR)激活，导致电压依赖性K*通道(Kv)抑制， 平滑肌(SM)细胞膜电位(Vm)去极化与电压依赖性钙增强 通道(Cav)活动。具体目标2将阐明星形细胞终末钙和大电导的作用 钙激活的K*(BK)通道在蛛网膜下腔出血(SAH)中的激活和抑制引起的血管收缩作用 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量变化的影响。 在活体内。包括双光子钙成像和去势、膜片钳在内的最新技术 电生理学、实时定量聚合酶链式反应和激光多普勒血流计被应用于 实验方法从亚细胞水平到完整的脑片和完整的动物。 该项目将与项目1密切合作(M.T.Nelson，脑切片成像和神经血管耦合； 功能性充血的活体测量)和项目2(J.E.Brayden、SM Cav和Vm研究)。此外， 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 学习。该项目将与M.Cipolla(项目3)互动，因为这些项目使用两种不同形式的模型 尽管中风的病因和最近的功能影响不同，但可能会有类似的 对神经血管耦合和认知功能的影响。这项工作将大大增加目前 关于蛛网膜下腔出血对PA功能和神经血管偶联作用的了解。这些研究还将 提供有助于识别这些病理的关键介质的指纹，并可能识别新的 治疗目标，以帮助将脑动脉瘤破裂的破坏性后果降至最低。

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.