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ORIGINAL RESEARCH article

Front. Cell. Neurosci.
Sec. Cellular Neurophysiology
Volume 18 - 2024 | doi: 10.3389/fncel.2024.1465216
This article is part of the Research Topic Cellular and Synaptic Mechanisms in the Auditory System in Health and Disease View all 9 articles

Noise-induced cochlear synaptopathy in C57BL/6N mice as a function of trauma strength: ribbons are more vulnerable than postsynapses

Provisionally accepted
Kerstin Blum Kerstin Blum Pauline Schepsky Pauline Schepsky Philip Derleder Philip Derleder Philipp Schätzle Philipp Schätzle Fahmi Nasri Fahmi Nasri Philipp Fischer Philipp Fischer Jutta Engel Jutta Engel *Simone Kurt Simone Kurt *
  • Department of Biophysics, Saarland University, Homburg, Germany

The final, formatted version of the article will be published soon.

    Noise-induced cochlear synaptopathy is characterized by irreversible loss of synapses between inner hair cells (IHC) and spiral ganglion neurons despite normal hearing thresholds. We analyzed hearing performance and cochlear structure in C57BL/6N mice that had been exposed to 100, 106 or 112 dB SPL broadband noise (8-16 kHz) for 2 h. Auditory brainstem responses (ABR) were assessed before, directly after and up to 28 days post trauma. Finally, number, size, and pairing of IHC presynaptic (CtBP2-positive) ribbons and postsynaptic AMPA receptor scaffold (HOMER-1-positive) clusters were analyzed along the cochlea. Four weeks after the 100 dB SPL trauma, a permanent threshold shift (PTS) was observed at 45 kHz, which after the higher traumata extended towards middle-to-lowfrequencies. Loss in amplitudes of ABR wave I amplitudes scaled with trauma strength indicating loss of functional IHC synaptic connections. Latencies of wave I mostly increased with trauma strength. No trauma-related OHC loss was found. Synaptic pairs were reduced in the midbasal and basal cochlear region in all trauma conditions with ribbon loss amounting up to 46 % of control. Ribbons surviving the trauma were paired whereas 4 -6 unpaired postsynapses/IHC were found in the medial, midbasal and basal region irrespective of trauma strength which contrasts findings in CBA/CaJ mice. Our data confirm the susceptibility of ribbon synapses and ABR wave I amplitudes to a noise trauma of 100 dB SPL or larger. Notably, peripheral dendrites bearing IHC postsynapses were less vulnerable than presynaptic ribbons in C57BL/6N mice.

    Keywords: Noise, cochlear synaptopathy, Hidden hearing loss, Hair cell, Ribbon, postsynapse, auditory nerve, ABR

    Received: 15 Jul 2024; Accepted: 12 Sep 2024.

    Copyright: © 2024 Blum, Schepsky, Derleder, Schätzle, Nasri, Fischer, Engel and Kurt. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

    * Correspondence:
    Jutta Engel, Department of Biophysics, Saarland University, Homburg, 66421, Germany
    Simone Kurt, Department of Biophysics, Saarland University, Homburg, 66421, Germany

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