title: Tuning of synapse number, structure and function in the cochlea.
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 Ca(2+) channel clusters and Ca(2+) 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 Ca(2+) signals, even within individual IHCs, providing a candidate presynaptic mechanism for the divergent dynamics of spiral ganglion neuron spiking.
authors.affiliation: InnerEarLab, Department of Otolaryngology and Center for Molecular Physiology of the Brain, University of Göttingen, Göttingen, Germany.
authors.forename: Alexander C
authors.initials: AC
authors.lastname: Meyer
authors.forename: Thomas
authors.initials: T
authors.lastname: Frank
authors.forename: Darina
authors.initials: D
authors.lastname: Khimich
authors.forename: Gerhard
authors.initials: G
authors.lastname: Hoch
authors.forename: Dietmar
authors.initials: D
authors.lastname: Riedel
authors.forename: Nikolai M
authors.initials: NM
authors.lastname: Chapochnikov
authors.forename: Yury M
authors.initials: YM
authors.lastname: Yarin
authors.forename: Benjamin
authors.initials: B
authors.lastname: Harke
authors.forename: Stefan W
authors.initials: SW
authors.lastname: Hell
authors.forename: Alexander
authors.initials: A
authors.lastname: Egner
authors.forename: Tobias
authors.initials: T
authors.lastname: Moser
mesh_terms: D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester / Q000494:pharmacology; D000161:Acoustic Stimulation / Q000379:methods; D000429:Alcohol Oxidoreductases; D000818:Animals; D000831:Animals, Newborn; D064026:Calbindins; D002118:Calcium / Q000378:metabolism; D002120:Calcium Channel Agonists / Q000494:pharmacology; D020746:Calcium Channels, L-Type / Q000378:metabolism; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology; D056970:Co-Repressor Proteins; D003051:Cochlea / Q000166:cytology* / Q000502:physiology*; D004268:DNA-Binding Proteins / Q000378:metabolism; D016057:Evoked Potentials, Auditory, Brain Stem / Q000502:physiology; D005089:Exocytosis / Q000187:drug effects / Q000502:physiology; D005849:Gerbillinae; D006199:Hair Cells, Auditory, Inner / Q000502:physiology* / Q000648:ultrastructure; D021962:Membrane Microdomains / Q000187:drug effects / Q000378:metabolism; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D051379:Mice; D008810:Mice, Inbred C57BL; D046529:Microscopy, Electron, Transmission; D018408:Patch-Clamp Techniques; D010750:Phosphoproteins / Q000378:metabolism; D011571:Psychoacoustics; D018091:Receptors, AMPA / Q000378:metabolism; D064030:S100 Calcium Binding Protein G / Q000378:metabolism; D013569:Synapses / Q000502:physiology* / Q000648:ultrastructure; D013997:Time Factors
chemical_list: C485995:Cacna1d protein, mouse; D064026:Calbindins; D002120:Calcium Channel Agonists; D020746:Calcium Channels, L-Type; D056970:Co-Repressor Proteins; D004268:DNA-Binding Proteins; D010750:Phosphoproteins; D018091:Receptors, AMPA; D064030:S100 Calcium Binding Protein G; D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; D000429:Alcohol Oxidoreductases; C111341:Ctbp2 protein, mouse; C104722:glutamate receptor ionotropic, AMPA 2; D002118:Calcium