Rama Sylvain, Jensen Thomas P, Rusakov Dmitri A
UCL Queen Square Institute of Neurology, University College London, London, United Kingdom.
Front Cell Neurosci. 2019 Jun 4;13:243. doi: 10.3389/fncel.2019.00243. eCollection 2019.
One of the most studied central synapses which have provided fundamental insights into cellular mechanisms of neural connectivity is the "giant" excitatory connection between hippocampal mossy fibers (MFs) and CA3 pyramidal cells. Its large presynaptic bouton features multiple release sites and is densely packed with thousands of synaptic vesicles, to sustain a highly facilitating "detonator" transmission. However, whether glutamate release sites at this synapse act independently, in a stochastic manner, or rather synchronously, remains poorly understood. This knowledge is critical for a better understanding of mechanisms underpinning presynaptic plasticity and postsynaptic signal integration rules. Here, we use the optical glutamate sensor SF-iGluSnFR and the intracellular Ca indicator Cal-590 to monitor spike-evoked glutamate release and presynaptic calcium entry in MF boutons. Multiplexed imaging reveals that distinct sites in individual MF giant boutons release glutamate in a probabilistic fashion, also showing use-dependent short-term facilitation. The present approach provides novel insights into the basic mechanisms of neurotransmitter release at excitatory synapses.
对神经连接的细胞机制提供了基本见解的研究最多的中枢突触之一，是海马苔藓纤维（MFs）与CA3锥体细胞之间的“巨大”兴奋性连接。其大的突触前终扣具有多个释放位点，并密集地排列着数千个突触小泡，以维持高度易化的“雷管”式传递。然而，该突触处的谷氨酸释放位点是独立、随机还是同步起作用，仍知之甚少。这一知识对于更好地理解突触前可塑性和突触后信号整合规则的基础机制至关重要。在这里，我们使用光学谷氨酸传感器SF-iGluSnFR和细胞内钙指示剂Cal-590来监测MF终扣中峰电位诱发的谷氨酸释放和突触前钙内流。多重成像显示，单个MF巨大终扣中的不同位点以概率方式释放谷氨酸，也表现出使用依赖性短期易化。本方法为兴奋性突触处神经递质释放的基本机制提供了新的见解。
