Tuning of synapse number, structure and function in the cochlea.
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.
Meyer
Alexander C
AC
InnerEarLab, Department of Otolaryngology and Center for Molecular Physiology of the Brain, University of Göttingen, Göttingen, Germany.
Frank
Thomas
T
Khimich
Darina
D
Hoch
Gerhard
G
Riedel
Dietmar
D
Chapochnikov
Nikolai M
NM
Yarin
Yury M
YM
Harke
Benjamin
B
Hell
Stefan W
SW
Egner
Alexander
A
Moser
Tobias
T
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
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