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Elementary properties of CaV1.3 Ca2+channels expressed in mouse cochlear inner hair cells

Authors :
Marlies Knipper
Stefan Münkner
Sergio Masetto
Neil D. Lawrence
Walter Marcotti
Valeria Zampini
Jacopo Magistretti
Christoph Franz
Jutta Engel
Stuart L. Johnson
Source :
The Journal of Physiology. 588:187-199
Publication Year :
2010
Publisher :
Wiley, 2010.

Abstract

Mammalian cochlear inner hair cells (IHCs) are specialized to process developmental signals during immature stages and sound stimuli in adult animals. These signals are conveyed onto auditory afferent nerve fibres. Neurotransmitter release at IHC ribbon synapses is controlled by L-type CaV1.3 Ca2+ channels, the biophysics of which are still unknown in native mammalian cells. We have investigated the localization and elementary properties of Ca2+ channels in immature mouse IHCs under near-physiological recording conditions. CaV1.3 Ca2+ channels at the cell pre-synaptic site co-localize with about half of the total number of ribbons present in immature IHCs. These channels activated at about −70 mV, showed a relatively short first latency and weak inactivation, which would allow IHCs to generate and accurately encode spontaneous Ca2+ action potential activity characteristic of these immature cells. The CaV1.3 Ca2+ channels showed a very low open probability (about 0.15 at −20 mV: near the peak of an action potential). Comparison of elementary and macroscopic Ca2+ currents indicated that very few Ca2+ channels are associated with each docked vesicle at IHC ribbon synapses. Finally, we found that the open probability of Ca2+ channels, but not their opening time, was voltage dependent. This finding provides a possible correlation between presynaptic Ca2+ channel properties and the characteristic frequency/amplitude of EPSCs in auditory afferent fibres.

Details

ISSN :
00223751
Volume :
588
Database :
OpenAIRE
Journal :
The Journal of Physiology
Accession number :
edsair.doi...........60e8f747949ee7a5eaabc1fcf2d04367
Full Text :
https://doi.org/10.1113/jphysiol.2009.181917