Acetylcholine, the first neurotransmitter identified more than a century ago, plays critical roles in human activities and health; however, its synaptic concentration dynamics have remained unknown. Here, we demonstrate the in situ simultaneous measurements of synaptic cholinergic transmitter concentration and release dynamics. We used nanoscale electroanalytical methods: nanoITIES electrode of 15 nm in radius and nanoresolved scanning electrochemical microscopy (SECM). Time-resolved in situ measurements unveiled information on synaptic acetylcholine concentration and release dynamics of living Aplysia neurons. The measuring technique enabled the quantitative sensing of acetylcholine with negligible interference of other ionic and redox-active species. We measured cholinergic transmitter concentrations very close to the synapse, with values as high as 2.4 mM. We observed diverse synaptic transmitter concentration dynamics consisting of singlet, doublet and multiplet events with a signal-to-noise ratio of 6 to 130. The unprecedented details about synaptic neurotransmission unveiled are instrumental for understanding brain communication and diseases in a way distinctive from extra-synaptic studies.

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活神经元胆碱能神经传递的单突触观察：浓度和动力学

乙酰胆碱是一个多世纪前发现的第一种神经递质，在人类活动和健康中起着至关重要的作用。然而，它的突触浓度动态仍然未知。在这里，我们展示了突触胆碱能递质浓度和释放动力学的原位同步测量。我们使用纳米级电分析方法：半径为 15 nm 的 nanoITIES 电极和纳米分辨扫描电化学显微镜 (SECM)。时间分辨原位测量揭示了有关活海兔神经元突触乙酰胆碱浓度和释放动力学的信息。该测量技术能够定量检测乙酰胆碱，而其他离子和氧化还原活性物质的干扰可忽略不计。我们测量了非常接近突触的胆碱能递质浓度，值高达 2.4 mM。我们观察到由信噪比为 6 到 130 的单线态、双线态和多线态事件组成的多种突触递质浓度动态。揭示的突触神经传递的前所未有的细节有助于以不同于外部的方式理解大脑通信和疾病。突触研究。