Abstract
A Ca2+ current transient block (ICaTB) by protons occurs at some ribbon-type synapses after exocytosis, but this has not been observed at mammalian hair cells. Here we show that a robust ICaTB occurs at post-hearing mouse and gerbil inner hair cell (IHC) synapses, but not in immature IHC synapses, which contain non-compact active zones, where Ca2+ channels are loosely coupled to the release sites. Unlike ICaTB at other ribbon synapses, ICaTB in mammalian IHCs displays a surprising multi-peak structure that mirrors the EPSCs seen in paired recordings. Desynchronizing vesicular release with intracellular BAPTA or by deleting otoferlin, the Ca2+ sensor for exocytosis, greatly reduces ICaTB, whereas enhancing release synchronization by raising Ca2+ influx or temperature increases ICaTB. This suggests that ICaTB is produced by fast multivesicular proton-release events. We propose that ICaTB may function as a submillisecond feedback mechanism contributing to the auditory nerve's fast spike adaptation during sound stimulation.
Original language | English (US) |
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Pages (from-to) | 3451-3464.e3 |
Journal | Cell Reports |
Volume | 25 |
Issue number | 12 |
DOIs | |
State | Published - Dec 18 2018 |
Keywords
- Ca channels
- auditory nerve fiber
- exocytosis
- inner hair cells
- otoferlin
- pH buffering
- protons
- ribbon synapses
ASJC Scopus subject areas
- General Biochemistry, Genetics and Molecular Biology