We found a match
Your institution may have rights to this item. Sign in to continue.
- Title
Calcium- and Otoferlin-Dependent Exocytosis by Immature Outer Hair Cells.
- Authors
Beurg, Maryline; Safieddine, Saaid; Roux, Isabelle; Bouleau, Yohan; Petit, Christine; Dulon, Didier
- Abstract
Immature cochlear outer hair cells (OHCs) make transient synaptic contacts (ribbon synapses) with type I afferent nerve fibers, but direct evidence of synaptic vesicle exocytosis is still missing. We thus investigated calcium-dependent exocytosis in murine OHCs at postnatal day 2 (P2)-P3, a developmental stage when calcium current maximum amplitude was the highest. By using time-resolved patch-clamp capacitance measurements, we show that voltage step activation of L-type calcium channels triggers fast membrane capacitance increase. Capacitance increase displayed two kinetic components, which are likely to reflect two functionally distinct pools of synaptic vesicles, a readily releasable pool (RRP; τ=79 ms) and a slowly releasable pool (τ=870 ms). The RRP size and maximal release rate were estimated at ~1200 vesicles and ~15,000 vesicles/s, respectively. In addition, we found a linear relationship between capacitance increase and calcium influx, like in mature inner hair cells (IHCs). These results give strong support to the existence of efficient calcium-dependent neurotransmitter release in immature OHCs. Moreover, we show that immature OHCs, just like immature IHCs, are able to produce regenerative calcium-dependent action potentials that could trigger synaptic exocytosis in vivo. Finally, the evoked membrane capacitance increases were abolished in P2-P3 OHCs from mutant Otof-/- mice defective for otoferlin, despite normal calcium currents. We conclude that otoferlin, the putative major calcium sensor at IHC ribbon synapses, is essential to synaptic exocytosis in immature OHCs too.
- Publication
Journal of Neuroscience, 2008, Vol 28, Issue 8, p1798
- ISSN
0270-6474
- Publication type
Article
- DOI
10.1523/JNEUROSCI.4653-07.2008