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Burst activity and ultrafast activation kinetics of Ca V 1.3 Ca 2+ channels support presynaptic activity in adult gerbil hair cell ribbon synapses

Authors :
Walter Marcotti
Matthew C. Holley
Valeria Zampini
Christoph Franz
Stuart L. Johnson
Sergio Masetto
Marlies Knipper
Jacopo Magistretti
Source :
The Journal of Physiology. 591:3811-3820
Publication Year :
2013
Publisher :
Wiley, 2013.

Abstract

Auditory information transfer to afferent neurons relies on precise triggering of neurotransmitter release at the inner hair cell (IHC) ribbon synapses by Ca2+ entry through CaV1.3 Ca2+ channels. Despite the crucial role of CaV1.3 Ca2+ channels in governing synaptic vesicle fusion, their elementary properties in adult mammals remain unknown. Using near-physiological recording conditions we investigated Ca2+ channel activity in adult gerbil IHCs. We found that Ca2+ channels are partially active at the IHC resting membrane potential (−60 mV). At −20 mV, the large majority (>70%) of Ca2+ channel first openings occurred with an estimated delay of about 50 μs in physiological conditions, with a mean open time of 0.5 ms. Similar to other ribbon synapses, Ca2+ channels in IHCs showed a low mean open probability (0.21 at −20 mV), but this increased significantly (up to 0.91) when Ca2+ channel activity switched to a bursting modality. We propose that IHC Ca2+ channels are sufficiently rapid to transmit fast signals of sound onset and support phase-locking. Short-latency Ca2+ channel opening coupled to multivesicular release would ensure precise and reliable signal transmission at the IHC ribbon synapse.

Details

ISSN :
14697793 and 00223751
Volume :
591
Database :
OpenAIRE
Journal :
The Journal of Physiology
Accession number :
edsair.doi...........4a21d38d563f5ee4a6478eee60d2d115
Full Text :
https://doi.org/10.1113/jphysiol.2013.251272