摘要
目的研究豚鼠Ⅱ型前庭毛细胞乙酰胆碱(acetylcholine,ACh)敏感性钾电流对钙离子的依赖性。方法应用全细胞膜片钳技术研究新鲜单离的豚鼠Ⅱ型前庭毛细胞ACh-敏感性钾电流在细胞内外钙离子浓度改变时其电流幅值的变化。结果①细胞外ACh激活一缓慢持久的外向性钾电流,其反转电位为(-70±10)mV;②ACh-敏感性钾电流电流对细胞外四乙胺(10mmol/L)敏感,而对细胞外4-氨基吡啶(100μmol/L)不敏感;③ACh-敏感性钾电流的幅值大小依赖于细胞外的钙离子浓度,无钙外液中ACh激活一很小的电流,4mmol/L外钙溶液中ACh-敏感性钾电流的幅值达到最大值,而0·5mmol/L外钙溶液中ACh-敏感性钾电流的幅值抑制至(36·5±6·5)%;④细胞内三磷酸肌醇-钙离子释放过程不参与ACh-敏感性钾电流的激活,细胞内透析肝素8mg/ml后30min,ACh-敏感性钾电流的幅值没有明显改变;⑤ACh敏感性钾电流对钙通道阻断剂Cd2+敏感。结论豚鼠Ⅱ型前庭毛细胞ACh-敏感性钾电流的激活依赖于细胞外的钙离子浓度,ACh与豚鼠Ⅱ型前庭毛细胞胆碱能受体结合后,首先激活膜上钙通道引起细胞外钙离子内流,毛细胞内游离钙离子浓度的升高进一步激活钙依赖性钾电流。
Objective To explore the dependence of Ca^2+ on the acetylcholine (ACh)-sensitive potassium current in guinea pig type Ⅱ vestibular hair cells. Methods Under the whole-cell patch mode, the current amplitude of the ACh-sensitive potassium current was recorded in response to the concentration change of the extracellular or intracellular Ca^2+. Results Following application of ACh, type II vestibular hair cells displayed the sustained potassium current, which was inhibited by tetraethylammonium chloride (TEA), but not inhibited by 4-aminopyride (4-AP). The activation of the ACh-sensitive potassium current was strongly affected by the concentration of the extracellular Ca^2+ . The current amplitude of the AChsensitive potassium increased following the increase of Ca^2+ concentration from 0 mmol/L to 4 mmol/L. At the concentration of 4 mmol/L Ca^2+ , the current amplitude of the ACh-sensitive potassium current reached the maximal response. Lowering the Ca^2+ concentration in the external solution from 4 mmol/L to 0. 5 mmol/L, the current amplitude of the ACh-sensitive potassium current was inhibited to ( 36. 5 ± 6. 5 ) %. However, no difference was found in the presence and in the absence of the intracellular heparin, which was a well-known blocker of the inositol trisphosphate-dependent calcium release channels. In addition, the calcium channel blocker, Cd^2+ , inhibited the ACh-sensitive potassium current. Conclusions The activation of the ACh- sensitive potassium current in guinea pig type Ⅱ vestibular hair cells was dependent on the extracellular Ca^2+ influx through the calcium channel. The application of ACh would stimulate membrane Ca^2+ channels; the influx of Ca^2+ will then activate the calcium-dependent potassium current in guinea pig type II hair cells to mediate the hyperpolarization effect.
出处
《中华耳鼻咽喉头颈外科杂志》
CAS
CSCD
北大核心
2006年第5期369-373,共5页
Chinese Journal of Otorhinolaryngology Head and Neck Surgery
基金
国家杰出青年科学基金资助项目(39925035)
国家自然科学基金资助项目(30070809
30371525)
国家"十五"科技攻关计划(2004BA720A18-02)
2004-2006卫生部临床学科重点项目资助
关键词
毛细胞
前庭
乙酰胆碱
钾
钙
Hair cells,vestibular
Acetylcholine
Potassium
Calcium