Synaptic Release Potentiation at Aging Auditory Ribbon Synapses

• DOI: 10.3389/fnagi.2021.756449
• Publication Date: 2021-10-18T05:38:56Z
• Authors: Thibault Peineau; Séverin Belleudy; Susanna Pietropaolo; Yohan Bouleau; Didier Dulon
• Keywords: Ribbon synapse

Age-related hidden hearing loss is often described as a cochlear synaptopathy that results from progressive degeneration of the inner hair cell (IHC) ribbon synapses. The functional changes occurring at these synapses during aging are not fully understood. Here, we characterized this process in IHCs C57BL/6J mice, strain which known to carry cadherin-23 mutation and experiences early with age. These while displaying large increase auditory brainstem thresholds due 50% IHC synaptic ribbons middle age (postnatal day 365), paradoxically showed enhanced acoustic startle reflex suggesting hyperacusis-like response. defect was associated shrinkage IHCs' body drastic enlargement their remaining presynaptic were facing enlarged postsynaptic AMPAR clusters. Presynaptic Ca2+ microdomains capacity sustain high rates exocytosis largely increased, on contrary expression fast-repolarizing BK channels, negatively control transmitter release, decreased. This age-related plasticity suggested potentiation transmission surviving synapses, could partially compensate decrease synapse number underlie hyperacusis.