Journal
ELIFE
Volume 11, Issue -, Pages -Publisher
eLIFE SCIENCES PUBL LTD
DOI: 10.7554/eLife.76008
Keywords
synaptic transmission; glutamate release; spontaneous release; evoked release; fluorescence photobleaching; iGluSnFR; Rat
Categories
Funding
- National Institute of Mental Health [MH66198, MH081060, MH070727]
- National Institute of General Medical Sciences [GM007347]
- Brain and Behavior Research Foundation
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This study used a fluorescent probe called iGluSnFR to investigate the organization of action potential-evoked and spontaneous neurotransmitter release within individual synapses. The results showed that action potential-evoked release is more susceptible to photobleaching, while spontaneous release is less affected.
Synapses maintain both action potential-evoked and spontaneous neurotransmitter release; however, organization of these two forms of release within an individual synapse remains unclear. Here, we used photobleaching properties of iGluSnFR, a fluorescent probe that detects glutamate, to investigate the subsynaptic organization of evoked and spontaneous release in primary hippocampal cultures. In nonneuronal cells and neuronal dendrites, iGluSnFR fluorescence is intensely photobleached and recovers via diffusion of nonphotobleached probes with a time constant of ~10 s. After photobleaching, while evoked iGluSnFR events could be rapidly suppressed, their recovery required several hours. In contrast, iGluSnFR responses to spontaneous release were comparatively resilient to photobleaching, unless the complete pool of iGluSnFR was activated by glutamate perfusion. This differential effect of photobleaching on different modes of neurotransmission is consistent with a subsynaptic organization where sites of evoked glutamate release are clustered and corresponding iGluSnFR probes are diffusion restricted, while spontaneous release sites are broadly spread across a synapse with readily diffusible iGluSnFR probes.
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