豚鼠Ⅱ型前庭毛细胞ACh-敏感性BK电流  

ACh-sensitive BK current in guinea pig type Ⅱ vestibular hair cells

作　　者：郭长凯[1] 余青松[1] 孔维佳[1] 李冠乔[1] 李擎天[1] 

机构地区：[1]华中科技大学同济医学院附属协和医院耳鼻咽喉科,湖北武汉430022

出　　处：《中国药理学通报》2006年第11期1334-1339,共6页Chinese Pharmacological Bulletin

基　　金：国家杰出青年科学基金资助项目(No39925035);国家自然科学基金资助项目(No3007708090;No30371515)

摘　　要：目的研究豚鼠球囊和椭圆囊Ⅱ型前庭毛细胞乙酰胆碱(ACh)-敏感性钾电流的特性。方法应用全细胞膜片钳技术检测新鲜单离的豚鼠球囊和椭圆囊Ⅱ型前庭毛细胞ACh-敏感性钾电流的离子特性及其药理学特点。结果①细胞外ACh激活一缓慢持久的外向性电流,其效应呈浓度依赖性,半数激活浓度为45μmol.L-1。②ACh-敏感性钾电流对钾通道阻断剂TEA(tetraethylammon ium)、IBTX(ibe-riotoxin)和Cs+敏感,而对4-AP(4-am inopyride)和apam in不敏感。③细胞内应用钙离子螯合剂BAPTA[b is(2-am inophe-noxy)ethane-N,N,N,′N-t′etra-acetic ac id],ACh-敏感性钾电流的幅值迅速被抑制。④ACh-敏感性钾电流对细胞外液中钙离子浓度变化敏感,0.2 mmol.L-1低钙外液中ACh-敏感性钾电流被抑制,电流最大值由0~10 mV向-20 mV^-30 mV超极化方向移动。结论细胞外ACh激活豚鼠球囊和椭圆囊Ⅱ型前庭毛细胞产生大电导钙依赖性钾电流(BK)。ACh-敏感性BK电流在豚鼠Ⅱ型前庭毛细胞超极化保护机制中具有重要的作用。Aim The nature of the α9-containing nicotinic ACh receptor （α9-nAChR）-mediated small-conductance, calcium-dependent potassium current （SK） in outer hair cells of guinea pigs and saccular hair cells of bullfrog was well-documented. Recently, we reported the slow and sustained calcium-dependent potassium current stimulated by ACh was located in type Ⅱ vestibular hair cells of guinea pigs. Therefore, the nature of the ACh-sensitive potassium current in type IIvestibular hair cells of guinea pig saccular macula and utricle macula was explored. Methods Under the whole-cell patch clamp mode, the pharmacology properties and the ions feature of the ACh-sensitive potassium current were investigated. Result Following extracellular perfusion of ACh, type Ⅱ vestibular hair cells displayed a slow and sustained outward current. The ACh-sensitive potassium current showed a dose-de pendent way with a half - activation concentration（EC50） of 45 μmol · L^-1 The ACh-sensitive potassium current was inhibited by extracellular TEA （tetraethylammonium, 5 mmol · L^-1 ）, potently inhibited by extracellular IBTX （iberiotoxin, 200 nmol · L^-1）, and completely abolished by intracellular Cs^＋. However, the ACh-sensitive potassium current was not sensitive to extracellular 4-AP（4-aminopyride, 15 μmol · L^-1 ） and apamin （ 1 μmol · L^-1 ）. The current amplitude of the ACh-sensitive potassium current was potently inhibited by intracellular application of BAPTA [bis （2-aminophenoxy ] ethane-N, N, N＇, N＇-tetra-acetic acid）. Furthermore, the ACh-sensitive potassium cur-rent was strongly inhibited by lowering of extracellular calcium concentration from 2 mmol · L^-1 to 0. 2 mmol · L^-1 with a maximum shifted toward hyperpolarized potential from 0- 10 mV to -20 mV- -30 mV. Conclusion Extracellular application of ACh activated the BK current. The ACh-sensitive BK current might play an important role in the synaptic inhibition of type Ⅱ vestibular hair cells of guinea pigs saccular macula and ut

关 键 词：前庭 毛细胞 乙酰胆碱 大电导钙依赖性钾电流 

分 类 号：R-332[医药卫生] R322.923