Multiplex imaging of quantal glutamate release and presynaptic Ca2+ at multiple synapses in situ

Thomas P. Jensen, Kaiyu Zheng, Nicholas Cole, Jonathan S. Marvin, Loren L. Looger, Dmitri A. Rusakov

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Jun 18, 2018
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Received: 1st June 18

Information processing by brain circuits depends on Ca2+-dependent, stochastic release of the excitatory neurotransmitter glutamate. Recently developed optical sensors have enabled detection of evoked and spontaneous release at common glutamatergic synapses. However, monitoring synaptic release probability, its use-dependent changes, and its underpinning presynaptic machinery in situ requires concurrent, intensity-independent readout of presynaptic Ca2+ and glutamate release. Here, we find that the red-shifted Ca2+ indicator Cal-590 shows Ca2+-sensitive fluorescence lifetime, and employ it in combination with the novel green glutamate sensor SF-iGluSnFR variant to document quantal release of glutamate together with presynaptic Ca2+ concentration, in multiple synapses in an identified neural circuit. At the level of individual presynaptic boutons, we use multi-exposure and stochastic reconstruction procedures to reveal nanoscopic co-localisation of presynaptic Ca2+ entry and glutamate release, a fundamental unknown in modern neurobiology. This approach opens a new horizon in the quest to understand release machinery of central synapses.

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This is an abstract of a preprint hosted on an independent third party site. It has not been peer reviewed but is currently under consideration at Nature Communications.

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