Pan-neuronal functional imaging and anesthesia

摘要 挥发性麻醉药产生全身麻醉的所有阶段，包括无意识、遗忘、镇痛 和肌肉放松。一旦进入这种生理状态，经验，记忆和身体 对剧痛的反应都消失了然而，我们仍然不理解这种状态是如何机械地 麻醉在神经元系统内产生，使得复杂的精神活动被消融， 生理机能得以保存。迄今为止，研究基本上沿着两条轨道进行沿着： 使用fMRI和EEG测量大脑整个区域的神经元活动（基本上是 受限于分辨率），或在分子水平上分析以寻找挥发性麻醉剂的特异性受体 （这在很大程度上是失败的）。令人惊讶的是，病人仍然可以迅速从这种状态中恢复过来， 经验性的临床实践已经降低了麻醉的风险， 现代医学实践中被普遍接受的一部分。幸运的是，使用新型荧光显微镜， 我们现在能够实时成像神经元活动，在体内，并在分辨率能够同时 捕捉单个神经元和复杂神经元网络的整个群体的活动。在本研究中， 我们将这种技术应用于C。我们能够捕捉到整个神经系统的活动， 以及我们捕获了躯体感觉皮层区域的老鼠。去辨别 临床麻醉是实现，这将是有意义的开始与最简单的，最听话的生物 已知麻醉是可诱导的神经元结构。C. elegans提供了一个简单的 神经系统（302个神经元），良好表征的行为范式和顺从的遗传学。此外，C. 线虫是麻醉学中公认的模型系统，并显示出不同的大体阶段， 在麻醉状态下的行为与人类相似。使用细胞内钙的荧光指示剂GCaMP 在神经元启动子下转基因表达的浓度，我们可以捕获多个 神经元的光学，非侵入性，和平行。我们的实验系统将允许我们测量 大规模神经元回路中的单个神经元，以了解离散神经元回路中的细微变化 神经元动力学导致在整个神经系统水平上的严重但可逆的功能缺陷 导致止痛和身体静止。我们的研究将确定挥发性麻醉剂的作用， 增加了从单个神经元到整个神经系统的神经元复杂性。现有技术 哺乳动物系统在规模上限于大脑的小部分。我们将开始互补 在小鼠的躯体感觉皮层中进行成像实验，这将启动我们的发现的翻译 和技术应用于哺乳动物系统。

Abstract Volatile anesthetics produce all stages of general anesthesia including unconsciousness, amnesia, analgesia and muscle relaxation. Once placed into this physiological state, the experience, memory and physical response to excruciating pain are all lost. However, we still do not understand mechanistically how this state of anesthesia is produced within neuronal systems such that complex mental activity is ablated while vestigial physiology is preserved. To date, research has proceeded along essentially two tracks: either the gross measurement of neuronal activity in entire regions of the brain using fMRI and EEG (which are fundamentally limited by resolution), or analysis at the molecular level looking for specific receptors for the volatile anesthetics (which has largely foundered). Astonishingly, patients can nevertheless be promptly retrieved from this state, and empirical clinical practice has reduced the risk of anesthesia to the extent that it is now an essential and universally accepted part of the modern practice of medicine. Fortunately, using novel fluorescent microscopy, we are now able to image neuronal activity in real-time, in vivo, and at resolutions capable of simultaneously capturing the activity of individual neurons and entire populations of complex neuronal networks. In this study, we apply this technique to C. elegans in which we are able to capture the activity of the entire nervous system, and to the mouse in which we capture regions of the somatosensory cortex. To discern the effect by which clinical anesthesia is achieved, it would make sense to begin with the creature with the simplest, most tractable neuronal architecture in which anesthesia is known to be inducible. C. elegans offers a simple well-mapped nervous system (302 neurons), well characterized behavioral paradigms and amenable genetics. Moreover C. elegans is well established as a model system in anesthesiology, and displays distinct stages of gross behavior under anesthesia similar to humans. Using GCaMP, a fluorescent indicator of intracellular calcium concentration expressed transgenically under a neuronal promoter, we can capture the activity of multiple neurons optically, non-invasively, and in parallel. Our experimental system will allow us to measure activity of the individual neurons within large-scale neuronal circuits to understand how subtle modifications in discrete neuronal dynamics lead to the gross but reversible functional defects at the level of the overall nervous system that result in analgesia and physical quiescence. Our study will define the effects of volatile anesthetics over increasing neuronal complexity from individual neurons to the entire nervous system. Current technology within mammalian systems is limited in scale to small subsections of the brain. We will begin complementary imaging experiments in the somatosensory cortex of the mouse that will initiate the translation of our findings and techniques to mammalian systems.