Acetylcholine-induced potassium current of guinea pig outer hair cells: Its dependence on a calcium influx through nicotinic-like receptors

被引:0
作者
Blanchet, C
Erostegui, C
Sugasawa, M
Dulon, D
机构
[1] INST NATL SANTE & RECH MED,LAB AUDIOL EXPT,F-33076 BORDEAUX,FRANCE
[2] UNIV BORDEAUX 2,HOP PELLEGRIN,F-33076 BORDEAUX,FRANCE
关键词
outer hair cell; Ca2+; acetylcholine; nicotinic receptor; Ca2+-activated K+ channel; caged-Ca2+; Fluo-3; patch clamp; confocal microscopy;
D O I
暂无
中图分类号
Q189 [神经科学];
学科分类号
071006 ;
摘要
The cholinergic efferent inhibition of mammalian outer hair cells (OHCs) is mediated by a hyperpolarizing K+ current. We have made whole-cell tight-seal recordings from single OHCs isolated from the guinea pig cochlea to characterize the mechanism by which acetylcholine (ACh) activates K+ channels. After ACh application, OHCs exhibited a biphasic response: an early depolarizing current preceding the predominant hyperpolarizing K+ current. The current-voltage (I-V) relationship of the ACh-induced response displayed an N-shape, suggesting the involvement of Ca2+ influx. When whole-cell recording was combined with confocal calcium imaging, we simultaneously observed the ACh-induced K+ current (I-K(ACh)) and a Ca2+ response restricted to the synaptic area of the cell. This I-K(ACh) could be prevented by loading OHCs with 10 mM of the fast Ca2+ buffer bis(2-aminophenoxy)ethane-N,N,N',N'-tetra-acetic acid (or BAPTA), therefore allowing the observation of the ACh-induced early current in isolation. This early current revealed nicotinic features because it activated with an intrinsic delay in the millisecond range, reversed nearly in between potassium and sodium equilibrium potentials, and was blocked by curare. However, it was strongly reduced in the absence of external Ca2+, and its I-V relationship displayed an unusual outward rectification at positive membrane potentials and an inward rectification below -60 mV. The results indicate that the cholinergic response of mammalian OHCs involves a ''nicotinic-like'' nonspecific cation channel through which Ca2+ enters and triggers activation of nearby Ca2+-dependent K+ channels.
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收藏
页码:2574 / 2584
页数:11
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