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This Article Full Text Full Text (PDF) All Versions of this Article: 567/1/67    most recent jphysiol.2005.089342v1 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 Autret, L. Articles by Desmadryl, G. Search for Related Content PubMed PubMed Citation Articles by Autret, L. Articles by Desmadryl, G.

¹ Institut des Neurosciences de Montpellier, INSERM U583, Hôpital Saint Eloi, 80 rue Augustin Fliche, 34091 Montpellier cedex 5, France
² Institut de Génomique Fonctionnelle, CNRS UMR 5203, INSERM U661, 141 rue de la Cardonille, 34094 Montpellier cedex 5, France

Ca²⁺ influx through voltage-gated calcium channels probably influences neuronal ontogenesis. Many developing neurones transiently express T-type/Ca_v3 calcium channels that contribute to their electrical activity and potentially to their morphological differentiation. Here we have characterized the electrophysiological properties and the functional role of a large T-type calcium current that is present in mouse developing primary vestibular neurones at embryonic day E17. This T-type current showed fast activation and inactivation, as well as slow deactivation kinetics. The overlap of activation and inactivation parameters produced a window current between –65 and –45 mV. Recovery from short-term inactivation was slow suggesting the presence of the Ca_v3.2 subunit. This T-type current was blocked by micromolar concentrations of Ni²⁺ and was inhibited by fast perfusion velocities in a similar fashion to recombinant Ca_v3.2 T-type channels expressed in HEK-293 cells. More importantly, current clamp experiments have revealed that the T-current could elicit afterdepolarization potentials during the repolarization phase of action potentials, and occasionally generate calcium spikes. Taken together, we demonstrate that the Ca_v3.2 subunit is likely to be the main T-type calcium channel subunit expressed in embryonic vestibular neurones and should play a key role in the excitability of these neurones during the ontogenesis of vestibular afferentation.

(Received 26 April 2005; accepted after revision 15 June 2005; first published online 16 June 2005)
Corresponding author G. Desmadryl: INSERM U583, INM, Hôpital Saint Eloi, 80 rue Augustin Fliche, 34091 Montpellier cedex 5, France. Email: desmad{at}univ-montp2.fr

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