THE TRANSDUCTION CHANNEL OF HAIR-CELLS FROM THE BULLFROG CHARACTERIZED BY NOISE-ANALYSIS
THE TRANSDUCTION CHANNEL OF HAIR-CELLS FROM THE BULLFROG CHARACTERIZED BY NOISE-ANALYSIS
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DOI：
10.1113/jphysiol.1986.sp016113
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发表时间：
1986-06-01
影响因子：
5.5
通讯作者：
HUDSPETH, AJ
中科院分区：
文献类型：
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作者：
HOLTON, T;HUDSPETH, AJ
用全细胞吉欧姆电压钳技术记录了牛蛙球囊上皮毛细胞对机械刺激的受体电流。刺激依赖的转导电流从细胞的刺激非依赖的K+和Ca~(2+)电流中分离出来，K~+电流被含Cs+的内液阻断，而Ca~(2+)电流则通过将膜电位控制在-70 mV以下而被抑制。该制剂的温度保持在10摄氏度左右，以减缓细胞转导通道的动力学。单个毛细胞的毛束的校准位移是用一个通过吸力连接到动毛纤毛球的探头进行的，并用一个压电双晶片刺激器移动。测头运动的均方根噪声小于2 nm。根据对毛束饱和(+/-0.5微米)位移的反应，测量受体电流的平均值I和方差Sigma 2。I校正了电流偏移量，Sigma 2校正了转导无关的背景方差。Sigma 2和I之间的关系与转导通道的两电导态模型的预测是一致的，该模型只有一个非零电导态。Sigma 2和I之间的关系可用方程Sigma 2=II-I2/N来拟合，其中N是细胞中的转导通道数，I是通过单个开放通道的电流。该转换通道的电导约为欧姆，反转电势接近0 mV。在10℃时，单个传导通道的估计电导为12.7+/-2.7ps(平均值+/-S.D.；n=18)。转导通道的数量N与Gmax成正比。在Gmax从0.08到2.48 ns的细胞中，N从7到280。N的最大值对应于每个立体纤毛有几个，也许是四个活跃的转导通道。对照实验表明，毛细胞对毛束刺激的两个人为来源的转导，即探头的噪声或不连续运动，对测量的方差Sigma 2没有实质性的贡献。位移-反应曲线通常是S型的和对称的；它们合理地符合包括一个开放状态和一个闭合状态的两个运动状态模型的预测。估计的位移敏感自由能Z为5.7+/-1.1千卡/摩尔微米(平均值+/-S.D.，n=18)。(摘要截断400字)
Receptor currents in response to mechanical stimuli were recorded from hair cells in the excised epithelium of the bull‐frog sacculus by the whole‐cell, gigohm‐seal voltage‐clamp technique. The stimulus‐dependent transduction current was separated from the cell's stimulus‐independent K+ and Ca2+ currents; the K+ currents were blocked with an internal solution containing Cs+ while the Ca2+ current was reduced by holding the membrane potential below ‐70 mV. The temperature of the preparation was maintained at about 10 degrees C to slow the kinetics of the cells' transduction channels. Calibrated displacements of hair bundles of individual hair cells were made with a probe coupled by suction to the kinociliary bulb and moved with a piezoelectricbimorph stimulator. The root mean square noise of probe motion was less than 2 nm. The mean, I, and the variance, sigma 2, of the receptor current were measured from the response to saturating (+/‐ 0.5 micron) displacements of the hair bundle. I was corrected for current offsets and sigma 2 for the transduction‐independent background variance. The relation between sigma 2 and I is consistent with the predictions of a two‐conductance‐state model of the transduction channel, a model having only one non‐zero conductance state. The relation between sigma 2 and I was fitted by the equation sigma 2 = Ii‐I2/N, where N is the number of transduction channels in the cell and i is the current through a single open channel. The conductance of the transduction channel is approximately ohmic with a reversal potential near 0 mV. The estimated conductance of a single transduction channel, gamma, is 12.7 +/‐ 2.7 pS (mean +/‐ S.D.; n = 18) at 10 degrees C. gamma is independent of the maximum transduction conductance of the cell, Gmax. The number of transduction channels, N, is proportional to Gmax. N ranges from 7 to 280 in cells with Gmax ranging from 0.08 to 2.48 nS. The largest values of N correspond to a few, perhaps four, active transduction channels per stereocilium. Control experiments show that transduction by the hair cell of two artifactual sources of hair‐bundle stimulation, noisy or discontinuous motion of the probe, do not contribute substantially to the measured variance, sigma 2. Displacement‐response curves are generally sigmoidal and symmetrical; they reasonably fit the predictions of a two‐kinetic‐state model, comprising one open state and one closed state. The estimated displacement‐sensitive free energy, Z, is 5.7 +/‐ 1.1 kcal/mol micron (mean +/‐ S.D., n = 18).(ABSTRACT TRUNCATED AT 400 WORDS)