Article abstract
Nature Neuroscience 12, 444 - 453 (2009)
Published online: 8 March 2009 | doi:10.1038/nn.2293
Tuning of synapse number, structure and function in the cochlea
Alexander C Meyer1,6, Thomas Frank1,6, Darina Khimich1,6, Gerhard Hoch1, Dietmar Riedel2, Nikolai M Chapochnikov1,3, Yury M Yarin1,4, Benjamin Harke5, Stefan W Hell5, Alexander Egner5 & Tobias Moser1,3
Abstract
Cochlear inner hair cells (IHCs) transmit acoustic information to spiral ganglion neurons through ribbon synapses. Here we have used morphological and physiological techniques to ask whether synaptic mechanisms differ along the tonotopic axis and within IHCs in the mouse cochlea. We show that the number of ribbon synapses per IHC peaks where the cochlea is most sensitive to sound. Exocytosis, measured as membrane capacitance changes, scaled with synapse number when comparing apical and midcochlear IHCs. Synapses were distributed in the subnuclear portion of IHCs. High-resolution imaging of IHC synapses provided insights into presynaptic Ca2+ channel clusters and Ca2+ signals, synaptic ribbons and postsynaptic glutamate receptor clusters and revealed subtle differences in their average properties along the tonotopic axis. However, we observed substantial variability for presynaptic Ca2+ signals, even within individual IHCs, providing a candidate presynaptic mechanism for the divergent dynamics of spiral ganglion neuron spiking.
- InnerEarLab, Department of Otolaryngology and Center for Molecular Physiology of the Brain, University of Göttingen, Göttingen, Germany.
- Laboratory of Electron Microscopy, Max-Planck-Institute for Biophysical Chemistry, Göttingen, Germany.
- Bernstein Center for Computational Neuroscience, University of Göttingen, Göttingen, Germany.
- Clinic of Otorhinolaryngology, Department of Medicine, Technical University of Dresden, Dresden, Germany.
- Department of NanoBiophotonics, Max-Planck-Institute for Biophysical Chemistry, Göttingen, Germany.
- These authors contributed equally to the work.
Correspondence to: Tobias Moser1,3 e-mail: tmoser@gwdg.de
Correspondence to: Alexander Egner5 e-mail: aegner@gwdg.de
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