Optogenetics and electron tomography for structure-function analysis of cochlear ribbon synapses

Chakrabarti, R. et al. (2023) Optogenetics and electron tomography for structure-function analysis of cochlear ribbon synapses. eLife, 11, e79494. (doi: 10.7554/elife.79494) (PMID:36562477) (PMCID:PMC9908081)

Abstract

Ribbon synapses of cochlear inner hair cells (IHCs) are specialized to indefatigably transmit sound information at high rates. To understand the underlying mechanisms, structure-function analysis of the active zone (AZ) of these synapses is essential. Previous electron microscopy studies of synaptic vesicle (SV) dynamics at the IHC AZ used potassium stimulation, which limited the temporal resolution to minutes. Here, we established optogenetic IHC stimulation followed by quick freezing within milliseconds and electron tomography to study the ultrastructure of functional synapse states with good temporal resolution in mice. We characterized optogenetic IHC stimulation by patch-clamp recordings from IHCs and postsynaptic boutons revealing robust IHC depolarization and neurotransmitter release. Ultrastructurally, the number of docked SVs increased upon short (17–25 ms) and long (48–76 ms) light stimulation paradigms. We did not observe enlarged SVs or other morphological correlates of homotypic fusion events. Our results indicate a rapid recruitment of SVs to the docked state upon stimulation and suggest that univesicular release prevails as the quantal mechanism of exocytosis at IHC ribbon synapses.

• Item Type: Articles
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Redondo Canales, Dr Magdalena
• Authors: Chakrabarti, R., María Jaime Tobón, L., Slitin, L., Redondo Canales, M., Hoch, G., Slashcheva, M., Fritsch, E., Bodensiek, K., Demet Özçete, Ö., Gültas, M., Michanski, S., Opazo, F., Neef, J., Pangrsic, T., Moser, T., and Wichmann, C.
• College/School: College of Medical Veterinary and Life Sciences > School of Psychology & Neuroscience
• Journal Name: eLife
• Publisher: eLife Sciences Publications
• ISSN: 2050-084X
• ISSN (Online): 2050-084X
• Published Online: 23 December 2022
• Copyright Holders: Copyright © 2022 Chakrabarti, Jaime Tobón, Slitin et al.
• First Published: First published in eLife 11:e79494
• Publisher Policy: Reproduced under a Creative Commons licence