HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Free via Open Access: OA OA Full Text Full Text (PDF) OA All Versions of this Article: 586/4/1029    most recent jphysiol.2007.145219v1 Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Johnson, S. L. Articles by Marcotti, W. Search for Related Content PubMed PubMed Citation Articles by Johnson, S. L. Articles by Marcotti, W. Related Collections Neuroscience Related Article

¹ Department of Biomedical Science, University of Sheffield, Sheffield S10 2TN, UK

The Ca²⁺ current (I_Ca) in prehearing and adult inner hair cells (IHCs), the primary sensory receptors of the mammalian cochlea, is mainly carried by L-type (Ca_V1.3) Ca²⁺ channels. I_Ca in immature and adult IHCs triggers the release of neurotransmitter onto auditory afferent fibres in response to spontaneous action potentials (APs) or graded receptor potentials, respectively. We have investigated whether the biophysical properties of I_Ca vary between low- and high-frequency IHCs during cochlear development and whether its inactivation influences cellular responses. I_Ca was recorded from gerbil IHCs maintained near physiological recording conditions. The size of I_Ca in adult IHCs was about a third of that in immature cells with no apparent difference along the cochlea at both stages. The activation kinetics of I_Ca were significantly faster in high-frequency IHCs, with that of adult cells being more rapid than immature cells. The degree of I_Ca inactivation was similar along the immature cochlea but larger in high- than low-frequency adult IHCs. This inactivation was greatly reduced with barium but not affected by changing the intracellular buffer (BAPTA instead of EGTA). Immature basal IHCs showed faster recovery of I_Ca from inactivation than apical cells allowing them to support a higher AP frequency. I_Ca in adult IHCs was more resistant to progressive inactivation following repeated voltage stimulation than that of immature cells. This suggests that adult IHCs are likely to be suited for sustaining rapid and repeated release of synaptic vesicles, which is essential for sound encoding.

(Received 18 September 2007; accepted after revision 11 December 2007; first published online 3 January 2008)
Corresponding author W. Marcotti: Department of Biomedical Science, University of Sheffield, Sheffield S10 2TN, UK. Email: w.marcotti{at}sheffield.ac.uk

Related Article

Gerbils can tune in

Jutta Engel
J. Physiol. 2008 586: 919. [Full Text] [PDF]

This article has been cited by other articles:

				S. L. Johnson, A. Forge, M. Knipper, S. Munkner, and W. Marcotti Tonotopic Variation in the Calcium Dependence of Neurotransmitter Release and Vesicle Pool Replenishment at Mammalian Auditory Ribbon Synapses J. Neurosci., July 23, 2008; 28(30): 7670 - 7678. [Abstract] [Full Text] [PDF]

				J. Engel Gerbils can tune in J. Physiol., February 15, 2008; 586(4): 919 - 919. [Full Text] [PDF]