Ohmori H
J Physiol. 1984 May;350:561-81. doi: 10.1113/jphysiol.1984.sp015218.
The ionic currents in enzymatically isolated vestibular hair cells of the chick were studied by a whole-cell-clamp variation of the patch voltage clamp, and by single channel recording. At membrane potentials more negative than -80 mV the hair cell showed anomalous rectification, and at potentials more positive than -40 mV large outward K currents were observed in normal saline. The outward K current decreased at large positive potentials, showing an N-shaped I-V relation. The outward K current was carried mostly through the Ca-activated K channel. K currents through the anomalous rectifier channel showed a decay in normal saline. This decay was eliminated reversibly in Na-free saline when the isotonic KCl-EGTA solution was used as the internal medium. However, a fast decay was still observed in Na-free high-K external solution when isotonic CaCl-EGTA was used as the internal medium. An increase in [K]o decreased the decay rate of the inward K current. The single-channel conductance of the anomalous rectifier channel was 50 pS in 160 mM-K saline and 23 pS in 40 mM-K saline. In 100 mM-Ca, -Sr and -Ba salines a large inward current was observed. At positive potentials the inward current carried by Ca and Sr ions showed significant decay; the current became outward at large positive potentials. Since the decay of the inward current was eliminated when 100 microM-quinine was added to the bathing medium, it was probably due to the activation of some Ca-activated K conductance which remained even with isotonic CsCl-EGTA internal medium. The activation kinetics of the Ca channel were studied in 100 mM-Ba solution at low temperatures (9-13 degrees C). From a comparison of the time constants of activation with the time constants of the tail currents, it was concluded that the Ca channel follows Hodgkin-Huxley-type m2 kinetics. A slow component that deviated from m2 kinetics was frequently observed at relatively large positive potentials. The steady-state fluctuations of Ba current showed a power density spectrum reasonably well fitted by a sum of two Lorentzian functions. The spectrum has a low-frequency component which indicates kinetics close to the macroscopic activation process of the Ca channel and a high-frequency component that indicates very fast flickering kinetics operating in the Ca channel.
采用膜片电压钳的全细胞钳制变体技术和单通道记录技术，对酶解分离的雏鸡前庭毛细胞中的离子电流进行了研究。在膜电位比 -80 mV 更负时，毛细胞表现出反常整流，而在电位比 -40 mV 更正时，在正常盐溶液中观察到较大的外向钾电流。外向钾电流在大的正电位时减小，呈现出 N 形的电流 - 电压关系。外向钾电流主要通过钙激活钾通道传导。通过反常整流通道的钾电流在正常盐溶液中表现出衰减。当使用等渗 KCl - EGTA 溶液作为内部介质时，在无钠盐溶液中这种衰减可逆地消除。然而，当使用等渗 CaCl - EGTA 作为内部介质时，在无钠高钾外部溶液中仍观察到快速衰减。细胞外钾离子浓度的增加降低了内向钾电流的衰减速率。反常整流通道的单通道电导在 160 mM - K 盐溶液中为 50 pS，在 40 mM - K 盐溶液中为 23 pS。在 100 mM - Ca、-Sr 和 -Ba 盐溶液中观察到较大的内向电流。在正电位时，由 Ca 和 Sr 离子携带的内向电流表现出明显的衰减；在大的正电位时电流变为外向。由于当向浴液中加入 100 μM 奎宁时内向电流的衰减被消除，所以这可能是由于即使在等渗 CsCl - EGTA 内部介质存在的情况下仍有一些钙激活钾电导被激活所致。在低温（9 - 13℃）下，在 100 mM - Ba 溶液中研究了钙通道的激活动力学。通过比较激活时间常数与尾电流时间常数，得出钙通道遵循霍奇金 - 赫胥黎型 m2 动力学。在相对较大的正电位时经常观察到偏离 m2 动力学的慢成分。钡电流的稳态波动显示出功率密度谱，该谱由两个洛伦兹函数之和合理地拟合。该谱有一个低频成分，表明其动力学接近钙通道的宏观激活过程，还有一个高频成分，表明在钙通道中存在非常快速的闪烁动力学。
