ACETYLCHOLINE ACTIVATES A K+ CONDUCTANCE PERMEABLE TO CS+ IN GUINEA-PIG OUTER HAIR-CELLS

被引:21
作者
EROSTEGUI, C
NENOV, AP
NORRIS, CH
BOBBIN, RP
机构
[1] DEPT OTORHINOLARYNGOL & BIOCOMMUN,KRESGE HEARING RES LAB S,NEW ORLEANS,LA 70112
[2] TULANE UNIV,SCH MED,DEPT OTOLARYNGOL,NEW ORLEANS,LA 70112
[3] LOUISIANA STATE UNIV,MED CTR,DEPT PHYSIOL,NEW ORLEANS,LA 70112
关键词
ION CHANNELS; BARIUM; CALCIUM; N-METHYLGLUCAMINE;
D O I
10.1016/0378-5955(94)90159-7
中图分类号
R36 [病理学]; R76 [耳鼻咽喉科学];
学科分类号
100104 ; 100213 ;
摘要
Acetylcholine (ACh), the major neurotransmitter released by efferent nerve fibers in the cochlea, has been shown to activate a Ca2+-dependent K+ conductance in outer hair cells (OHCs). Previously we reported that this ACh operated conductance is permeable to Cs+. The purpose of the present study was to characterize further this Cs+-permeable channel and its dependency on Ca2+ using isolated OHCs and the patch clamp technique in the whole cell configuration. The changes in the ACh response were examined when Cs+, Ba2+, Cd2+, N-methyl-D-glucamine (NMG(+)) and tetraethylammonium (TEA(+)) were placed in the external or internal solutions. Cs+ substituted for K+ in carrying the ACh-evoked Ca2+-dependent K+ current. When NMG(+)\TEA(+) was substituted for internal K+ ACh-evoked an inward and an outward current, and Cs+ substituted for external K+ blocked the outward but not the inward current evoked by ACh suggesting it was carried by K+. In the NMG(+)\TEA(+) condition, when the cell was held at different V-h values for an extended period of time, the ACh-induced K+ current rectified. In Ba2+ (3 mM) with zero Ca2+ ACh failed to induce any detectable current and the ACh response slowly recovered from the Ba2+ block, suggesting a block at an intracellular site. Cd2+ (1 mM) readily and reversibly blocked ACh-induced currents even when carried by Cs+. This data suggests that ACh opens a channel selective for K+, conductive to Cs+ and dependent on Ca2+.
引用
收藏
页码:119 / 129
页数:11
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