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A calcium-activated nonselective cationic channel in the basolateral membrane of outer hair cells of the guinea-pig cochlea
Authors:Thierry Van den Abbeele  Patrice Tran Ba Huy  Jacques Teulon
Affiliation:(1) Faculté de médecine Necker-Enfants Malades, INSERM U.323, 156 rue de Vaugirard, F-75015 Paris, France;(2) Faculté de médecine Lariboisière, Laboratoire d'otologie expérimentale, 10 avenue de Verdun, F-7501 Paris, France
Abstract:The patch-clamp technique was used to investigate ion channels in the basolateral perilymph-facing membrane of freshly isolated outer hair cells (OHCs) from the guinea-pig cochlea. These sensory cells probably determine, via their motile activity, the fine tuning of sound frequencies and the high sensitivity of the inner ear. A Ca2+-activated nonselective cationic channel was found in excised inside-out membrane patches. The current/voltage relationship was linear with a unit conductance of 26.3±0.3 pS (n=15) under symmetrical inger conditions. The channel excluded anions (PNa/PCl=18 wherePNa/PCl denotes the relative permeability of Na to Cl); it was equally permeant to the Na+ and K+ ions and exhibited a low permeability toN-methyl-D-glucamine and Ba2+ or Ca2+. Channel opening required a free Ca2+ concentration of about 10–6 mol/l on the internal side of the membrane and the open probability (Po) was maximal at 10–3 mol/l (Po=0.72±0.06,n=12). Adenosine 5primemono-, tri- and di-phosphate reducedPo to 29±14 (n=5), 42±10 (n=8) and 51±12 (n=5) % of controlPo, respectively, when they were added at a concentration of 10–3 mol/l to the internal side. The channel was partially blocked by flufenamic acid (10–4 mol/l) and 3prime,5prime-dichlorodiphenylamine-2-carboxylic acid (DCDPC, 10–5 mol/l). This type of channel, together with Ca2+-activated K+ channels, might participate in the control of membrane potential and modulate the motility of OHCs.
Keywords:Inner ear  Hair cells  Patch-clamp  Nonselective cationic channels
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