Inverse neurovascular coupling in the hypothalamus and its role in positive feedback regulation of Vasopressin neurons in health and disease

神经血管偶联(NVC)链接增加了神经元的活动，并具有快速和空间受限的增加 在局部血液流动中。关于驱动NVC的细胞机制的知识主要集中在瞬变 外部感受性感觉刺激，仅限于大脑背侧浅层区域(皮质)。因此，人们对此了解较少。 慢、持续、大范围刺激可激活的脑深部NVC动力学研究 (例如，身体动态平衡的生理紊乱)。动态平衡过程中的紊乱是一个关键驱动因素 研究流行疾病的病理机制，如心力衰竭(HF)中的神经体液激活。至 为了解决我们知识中的这一关键差距，我们开发了一种新的实验方法，使 在挑战身体动态平衡的过程中，内感诱导的NVC。我们的初步数据显示，与 典型的NVC反应，一种系统性和生理性的动态平衡挑战(急性盐负荷) 进行性增加的加压素(VP)神经元放电，诱发的活动依赖的血管收缩和 下丘脑视上核(SON)局部血流量减少。盐诱导的逆NVC(INVC) 反应缓慢、持续和广泛，并由SON内VP的树突释放所介导。 INVC引起局部组织缺氧，引起VP神经元的进一步兴奋。基于这些 根据观察，我们假设iNVC是一个有助于正面反馈的生理过程 调节VP神经元的数量，从而使生理障碍得到有效纠正。不过， NVC这种新的生理模式的确切信号机制和细胞靶点，以及 更重要的是，iNVC反应异常是否导致VP神经元活动加剧 普遍的心脏代谢性疾病的特征，如心衰，仍不清楚。使用多学科 方法，在目标1中，我们将阐明介导活动的精确信号机制和细胞靶标- SON中依赖的iNVC(神经元到血管的信号)。在目标2中，我们将确定机制和 INVC诱发VP神经元放电活动正反馈调制的靶点 神经元信号)。最后，在Aim3中，我们将阐明导致iNVC介导的加重的机制 疾病状态下VP神经元的正反馈调节。体内和体外的新方法 (双光子成像、膜片钳电生理学和儿子小动脉的体外插管)将用于 新型转基因大鼠模型能够可视化(EGFP)和操纵(光和化学遗传学) SON内的VP神经元。酸敏感离子通道的激活与星形胶质细胞的调控 谷氨酸转运体将被作为关键的分子靶标进行研究。我们期待这项工作的成果 有助于更好地理解不同大脑中NVC反应的基本机制 在不同的区域和不同的依赖活动的模式下。此外，我们预计我们的研究将揭开小说的面纱 高发心脏代谢性疾病的病理机制和治疗靶点。 1

Neurovascular coupling (NVC) links increases in neuronal activity with a rapid and spatially restricted increase in local blood flow. Knowledge on the cellular mechanisms driving NVC has been focused on transient exteroceptive sensory stimulation and limited to superficial dorsal brain areas (cortex). Thus, less is understood on NVC dynamics of deeper brain regions, which can be activated by slow, sustained, and widespread stimuli (e.g., physiological disturbances of bodily homeostasis). Derangement in homeostatic processes is a key driver of pathological mechanisms in prevalent diseases such as neurohumoral activation in heart failure (HF). To address this critical gap in our knowledge, we developed a novel experimental approach that enables interoceptive-induced NVC during a challenge to bodily homeostasis. Our preliminary data show that contrary to the canonical NVC response, a systemic and physiological homeostatic challenge (acute salt-loading) progressively increased vasopressin (VP) neuronal firing, evoked activity-dependent vasoconstriction and decreased local blood flow in the hypothalamic supraoptic nucleus (SON). The salt-induced inverse NVC (iNVC) response was slow, sustained and widespread, and mediated by the dendritic release of VP within the SON. iNVC resulted in local tissue hypoxia, which evoked further excitation of VP neurons. Based on these observations, we hypothesize that iNVC is a physiological process that contributes to positive feedback modulation of the VP neuronal population so that the physiological disturbance can be efficiently corrected. Still, the precise signaling mechanisms and cellular targets mediating this novel physiological modality of NVC, and more importantly, whether an aberrant iNVC response contributes to exacerbated VP neuronal activity characteristic of prevalent cardiometabolic diseases, such as HF, remains unknown. Using a multidisciplinary approach, in Aim 1 we will elucidate the precise signaling mechanisms and cellular targets mediating activity- dependent iNVC in the SON (neuron-to-vessel signaling). In Aim 2, we will determine the mechanisms and targets by which the iNVC evokes the positive feedback modulation of VP neuronal firing activity (vasculo-to- neuron signaling). Finally, in Aim3, we will elucidate mechanisms contributing to exacerbated iNVC-mediated positive feedback regulation of VP neurons in a disease state (HF). Both in vivo and ex vivo novel approaches (2-photon imaging, patch-clamp electrophysiology, and ex vivo cannulation of SON arterioles) will be used in novel transgenic rat models that enable visualization (eGFP) and manipulation (opto- and chemogenetically) of VP neurons in the SON. The activation of acid-sensing ion channels (ASIC) and modulation of astrocyte glutamate transporters will be investigated as key molecular targets. We expect results from this work to contribute to a better understanding of fundamental mechanisms underlying NVC responses in different brain regions and under different activity-dependent modalities. Moreover, we anticipate our studies to unveil novel pathological mechanisms and therapeutic targets for the treatment of highly prevalent cardiometabolic diseases. 1