Kinetics of Exocytosis and Endocytosis at the Cochlear Inner Hair Cell Afferent Synapse of the Mouse

Hearing in mammals relies on the highly synchronous synaptic transfer between cochlear inner hair cells (IHCs) and the auditory nerve. We studied the presynaptic function of single mouse IHCs by monitoring membrane capacitance changes and voltage-gated Ca2+currents. Exocytosis initially occurred at...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 2000-01, Vol.97 (2), p.883-888
Main Authors: Moser, Tobias, Beutner, Dirk
Format: Article
Language:English
Subjects:
Animals
Auditory nerve
Biological Sciences
Calcium - metabolism
Calcium - pharmacology
Cochlea - physiology
Depolarization
Ears & hearing
Electric Conductivity
Electric Stimulation
Endocytosis
Evoked Potentials, Auditory - drug effects
Exocytosis
Hair cells
Hair Cells, Auditory, Inner - cytology
Hair Cells, Auditory, Inner - physiology
Inner hair cells
Kinetics
Mice
Neurology
Neurons
Neurons, Afferent - physiology
Neuroscience
Patch-Clamp Techniques
Rodents
Synapses
Synapses - physiology
Synaptic Vesicles - physiology
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Summary:Hearing in mammals relies on the highly synchronous synaptic transfer between cochlear inner hair cells (IHCs) and the auditory nerve. We studied the presynaptic function of single mouse IHCs by monitoring membrane capacitance changes and voltage-gated Ca2+currents. Exocytosis initially occurred at a high rate but then slowed down within a few milliseconds, despite nearly constant Ca2+influx. We interpret the observed secretory depression as depletion of a readily releasable pool (RRP) of about 280 vesicles. These vesicles are probably docked close to Ca2+channels at the ribbon-type active zones of the IHCs. Continued depolarization evoked slower exocytosis occurring at a nearly constant rate for at least 1 s and depending on "long-distance" Ca2+signaling. Refilling of the RRP after depletion followed a biphasic time course and was faster than endocytosis. RRP depletion is discussed as a mechanism for fast auditory adaptation.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.97.2.883