A remaining challenge for genetically encoded voltage indicators (GEVIs) is the reliable detection of excitatory postsynaptic potentials (EPSPs). Here, we developed ASAP5 as a GEVI with enhanced activation kinetics and responsivity near resting membrane potentials for improved detection of both spiking and subthreshold activity. ASAP5 reported action potentials (APs) in vivo with higher signal-to-noise ratios than previous GEVIs and successfully detected graded and subthreshold responses to sensory stimuli in single two-photon trials. In cultured rat or human neurons, somatic ASAP5 reported synaptic events propagating centripetally and could detect ∼1-mV EPSPs. By imaging spontaneous EPSPs throughout dendrites, we found that EPSP amplitudes decay exponentially during propagation and that amplitude at the initiation site generally increases with distance from the soma. These results extend the applications of voltage imaging to the quantal response domain, including in human neurons, opening up the possibility of high-throughput, high-content characterization of neuronal dysfunction in disease.

中文翻译：

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快速响应的电压指示器，对单一突触事件具有更高的灵敏度


基因编码电压指示剂 （GEVI） 的另一个挑战是兴奋性突触后电位 （EPSP） 的可靠检测。在这里，我们将 ASAP5 开发为一种 GEVI，在静息膜电位附近具有增强的激活动力学和响应性，以改善对尖峰和亚阈值活性的检测。ASAP5 报告了体内动作电位 （AP） 具有比以前的 GEVI 更高的信噪比，并在单双光子试验中成功检测到对感觉刺激的分级和亚阈值反应。在培养的大鼠或人类神经元中，体细胞 ASAP5 报告了向心传播的突触事件，并且可以检测到 ∼1 mV EPSP。通过对整个树突中的自发 EPSP 进行成像，我们发现 EPSP 振幅在传播过程中呈指数衰减，并且起始位点的振幅通常随着与体细胞的距离而增加。这些结果将电压成像的应用扩展到量子响应域，包括在人类神经元中，为疾病中神经元功能障碍的高通量、高内涵表征开辟了可能性。