Journal
EMBO JOURNAL
Volume 40, Issue 5, Pages -Publisher
WILEY
DOI: 10.15252/embj.2020106010
Keywords
calcium channel; exocytosis; nanodomain; synaptic heterogeneity; wide dynamic range coding
Categories
Funding
- Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) under Germany's Excellence Strategy [EXC 2067/1-390729940]
- Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) via collaborative research center [889, 1286]
- ProjektDEAL
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This study investigated the transfer function of synapses in inner hair cells, finding that differences in voltage dependence and release site coupling can affect synaptic transmission, contributing to the functional diversity of spiral ganglion neurons. The reported mechanism may help sensory cells and neurons in general to diversify signaling, even in nearby synapses.
The cochlea encodes sound pressures varying over six orders of magnitude by collective operation of functionally diverse spiral ganglion neurons (SGNs). The mechanisms enabling this functional diversity remain elusive. Here, we asked whether the sound intensity information, contained in the receptor potential of the presynaptic inner hair cell (IHC), is fractionated via heterogeneous synapses. We studied the transfer function of individual IHC synapses by combining patch-clamp recordings with dual-color Rhod-FF and iGluSnFR imaging of presynaptic Ca2+ signals and glutamate release. Synapses differed in the voltage dependence of release: Those residing at the IHC' pillar side activated at more hyperpolarized potentials and typically showed tight control of release by few Ca2+ channels. We conclude that heterogeneity of voltage dependence and release site coupling of Ca2+ channels among the synapses varies synaptic transfer within individual IHCs and, thereby, likely contributes to the functional diversity of SGNs. The mechanism reported here might serve sensory cells and neurons more generally to diversify signaling even in close-by synapses.
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