Two types of voltage-dependent potassium channels in outer hair cells from the guinea pig cochlea.
Cell-attached and cell-free configurations of the patch-clamp technique were used to investigate the conductive properties and regulation of the major K(+) channels in the basolateral membrane of outer hair cells freshly isolated from the guinea pig cochlea. There were two major voltage-dependent K(+) channels. A Ca(2+)-activated K(+) channel with a high conductance (220 pS, P(K)/P(Na) = 8) was found in almost 20% of the patches. The inside-out activity of the channel was increased by depolarizations above 0 mV and increasing the intracellular Ca(2+) concentration. External ATP or adenosine did not alter the cell-attached activity of the channel. The open probability of the excised channel remained stable for several minutes without rundown and was not altered by the catalytic subunit of protein kinase A (PKA) applied internally. The most frequent K(+) channel had a low conductance and a small outward rectification in symmetrical K(+) conditions (10 pS for inward currents and 20 pS for outward currents, P(K)/P(Na) = 28). It was found significantly more frequently in cell-attached and inside-out patches when the pipette contained 100 microM acetylcholine. It was not sensitive to internal Ca(2+), was inhibited by 4-aminopyridine, was activated by depolarization above -30 mV, and exhibited a rundown after excision. It also had a slow inactivation on ensemble-averaged sweeps in response to depolarizing pulses. The cell-attached activity of the channel was increased when adenosine was superfused outside the pipette. This effect also occurred with permeant analogs of cAMP and internally applied catalytic subunit of PKA. Both channels could control the cell membrane voltage of outer hair cells.
van Den Abbeele
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Laboratoire de Neurobiologie des Systèmes Sensori-moteurs, Unité Propre de Recherche et de l'Enseignement Supérieur 7060, France. thierry.van-den-abbeele@rdb.ap-hop-paris.fr
Teulon
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J
Huy
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PT
D015761:4-Aminopyridine / Q000494:pharmacology; D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D000109:Acetylcholine / Q000494:pharmacology; D000241:Adenosine / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000494:pharmacology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D051668:Delayed Rectifier Potassium Channels; D004553:Electric Conductivity; D004558:Electric Stimulation; D006168:Guinea Pigs; D018072:Hair Cells, Auditory, Outer / Q000737:chemistry* / Q000201:enzymology*; D015640:Ion Channel Gating / Q000187:drug effects / Q000502:physiology*; D007700:Kinetics; D051036:Large-Conductance Calcium-Activated Potassium Channels; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D018408:Patch-Clamp Techniques; D011188:Potassium / Q000493:pharmacokinetics; D015221:Potassium Channels / Q000502:physiology*; D024681:Potassium Channels, Calcium-Activated; D024642:Potassium Channels, Voltage-Gated; D051640:Small-Conductance Calcium-Activated Potassium Channels
D051668:Delayed Rectifier Potassium Channels; D051036:Large-Conductance Calcium-Activated Potassium Channels; D015221:Potassium Channels; D024681:Potassium Channels, Calcium-Activated; D024642:Potassium Channels, Voltage-Gated; D051640:Small-Conductance Calcium-Activated Potassium Channels; D015124:8-Bromo Cyclic Adenosine Monophosphate; D000255:Adenosine Triphosphate; D015761:4-Aminopyridine; D017868:Cyclic AMP-Dependent Protein Kinases; D000241:Adenosine; D000109:Acetylcholine; D011188:Potassium; D002118:Calcium