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This Article Full Text Full Text (PDF) All Versions of this Article: 96/2/602    most recent 01315.2005v1 Alert me when this article is cited Alert me if a correction is posted Citation Map 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 Google Scholar Google Scholar Articles by Zampini, V. Articles by Masetto, S. Search for Related Content PubMed PubMed Citation Articles by Zampini, V. Articles by Masetto, S.

Single-Channel L-Type Ca²⁺ Currents in Chicken Embryo Semicircular Canal Type I and Type II Hair Cells

Dipartimento di Scienze Fisiologiche-Farmacologiche Cellulari-Molecolari, Sez. di Fisiologia Generale e Biofisica Cellulare, Università di Pavia, Pavia, Italy

Submitted 14 December 2005; accepted in final form 27 April 2006

Few data are available concerning single Ca channel properties in inner ear hair cells and particularly none in vestibular type I hair cells. By using the cell-attached configuration of the patch-clamp technique in combination with the semicircular canal crista slice preparation, we determined the elementary properties of voltage-dependent Ca channels in chicken embryo type I and type II hair cells. The pipette solutions included Bay K 8644. With 70 mM Ba²⁺ in the patch pipette, Ca channel activity appeared as very brief openings at –60 mV. Ca channel properties were found to be similar in type I and type II hair cells; therefore data were pooled. The mean inward current amplitude was –1.3 ± 0.1 (SD) pA at – 30 mV (n = 16). The average slope conductance was 21 pS (n = 20). With 5 mM Ba²⁺ in the patch pipette, very brief openings were already detectable at –80 mV. The mean inward current amplitude was –0.7 ± 0.2 pA at –40 mV (n = 9). The average slope conductance was 11 pS (n = 9). The mean open time and the open probability increased significantly with depolarization. Ca channel activity was still present and unaffected when -agatoxin IVA (2 µM) and -conotoxin GVIA (3.2 µM) were added to the pipette solution. Our results show that types I and II hair cells express L-type Ca channels with similar properties. Moreover, they suggest that in vivo Ca²⁺ influx might occur at membrane voltages more negative than –60 mV.