豚鼠耳蜗外毛细胞乙酰胆碱敏感性钾电流特性  

Feature of ACh-sensitive potassium current in outer hair cells of guinea pig cochlea

作　　者：郭长凯[1] 孔维佳[1] 余青松[1] 李冠乔[1] 李家荔[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,武汉430022

出　　处：《中华耳鼻咽喉头颈外科杂志》2007年第4期286-290,共5页Chinese Journal of Otorhinolaryngology Head and Neck Surgery

基　　金：国家自然科学基金(30070809;30371525;30672309);国家"十五"科技攻关计划(2004BA720A1802);国家杰出青年科学基金(39925035);卫生部临床学科重点项目(2004-2006)

摘　　要：目的研究豚鼠耳蜗外毛细胞乙酰胆碱(acetylcholine,ACh)敏感性钾电流离子特性及其受体的药理学特性。方法健康豚鼠38只,断头后取出基底膜,经胶原酶Ⅳ消化后获取外毛细胞。采用全细胞记录膜片钳技术检测新鲜单离外毛细胞 ACh-敏感性钾电流对细胞外钙依赖性钾电流阻断剂和 N 型胆碱能受体抑制剂的敏感性。结果①细胞外 ACh 激活一快速去敏感化的外向性钾电流,其平均(±s,以下同)反转电位为(-67.3±8.2)mV(n=10);-50 mV 钳制电压下,100μmol/LACh 激活电流的幅值为(506.6±186.3)pA(n=9)。②ACh-敏感性钾电流对细胞外四乙铵(tetraethylammonium,TEA,10 mmol/L)、蜂毒明肽(apamin,1μmol,/L)敏感,而细胞外的 IBTX(iberiotoxin,200 nmol/L)对 ACh-敏感性钾电流幅值无抑制作用。③ACh-敏感性钾电流的半数激活浓度(EC_(50))为(33.5±5.7)μmoL/L(n=7)。④ACh-敏感性钾电流对细胞外γ-氨基丁酸(gamma-aminobutyric acid,GABA)-A 受体阻断剂荷包牡丹碱(bicuculline)和α9-N 型胆碱能受体(α9受体)特异性抑制剂士的宁(strychnine)敏感。士的宁和荷包牡丹碱对 ACh-敏感性钾电流的抑制作用具有浓度依赖性,其半数抑制浓度(IC_(50))分别为(22.3±2.6)nmol/L(n=7)和(1_2±0.4)μmol/L(n=6)。结论细胞外 ACh 激活豚鼠耳蜗外毛细胞产生小电导钙依赖性钾电流(SK),此电流可能由α9受体介导。Objective To explore the feature of the ACh-sensitive potassium current in guinea pig cochlear outer hair cells. Methods Cochlear outer hair cells of guinea pigs （ n = 38 ） were isolated by collagenase type IV. Under the whole-cell patch mode, the ions nature and the pharmacological properties of the ACh-sensitive potassium current were investigated by applying the inhibitors of calcium-dependent potassium currents and the inhibitors of nicotinic ACh receptor. Results Following application of ACh, cochlear outer hair cells displayed a rapidly activating outward potassium current with a fast desensitized kinetic and a reversal （x^- ± s） potential of （ - 67. 3 ± 8. 2 ） mV （ n = 10 ）. At the holding potential of - 50 mV, the current amplitude of ACh-sensitive potassium current activated by 100 μmol/L ACh was （506. 6 ± 186. 3 ） pA（ n = 9 ）. ACh-sensitive potassium current was sensitive to TEA （tetraethylammonium chloride, 10 mmol/L） and potently inhibited by the small conductance calcium-dependent potassium current （SK） blocker, apamin （1 μmol/L）. Iberiotoxin （IBTX）, the well-known blocker of big conductance calcium-dependent potassium current （ BK）, failed to inhibit the amplitude of the ACh-sensitive potassium current at the dose of 200 nmol/L. The dose for half-maximal response （ EC50 ） of the ACh-sensitive potassium current was （33.5 ± 5.7 ） μmol/L （ n = 7 ） . The ACh-sensitive potassium current was sensitive to the GABA （gamma-aminobutyric acid）-A receptor blocker, bicuculline, and strongly inhibited by the selective blocker of the α 9-nicotinic ACh receptor, strychnine. Strychnine and bicuculline showed the dose-dependent blocking effect with a half inhibition-maximal response （IC50） of （22. 3 ±2. 6）nmol/L（n =7） and （ 1.2 ±0.4） μmol/L （n = 6 ）, respectively. Conclusions This work provides direct evidences that the ACh-sensitive SK current was present on guinea pig cochlear outer hair cells. The activation of the ACh-sensi

关 键 词：毛细胞 外 受体 胆碱能 膜片钳术 

分 类 号：R764[医药卫生—耳鼻咽喉科]