CELLULAR BASIS OF TUNING IN THE COCHLEA

这项拟议研究的目标是描述细胞的特性 有助于海龟耳蜗毛细胞调谐的机制。 通过了解这些细胞机制如何有助于 频率选择性，我们将能够评估它们的局限性 以及包括人类在内的高等脊椎动物对听力的适用性。 全细胞膜片钳与单通道膜片钳的结合 这项技术将用于从已鉴定的 海龟耳蜗区。第一个目标是分析 毛细胞纤毛束的机械反应，并 确定这种反应在整个转导中的作用 机制。电源、强度和电压敏感度 纤毛运动将被确定。换能器的能力 检测此运动的通道将被确定，并且任何 尺寸和电压敏感度随特性的变化 将评估频率。第二个目标是描述 此外，基底外侧毛细胞膜中的电导 牵涉到电波共振。大小和尺寸的变化 已知细胞膜电流的动力学研究 特征频率将使用小区内分析 灌流。特定协议解决了向内隔离的问题 由根尖换能器和基底外侧钙引起的电流 电流，可能的电生输运的表征 钙从细胞中排出，并从细胞中分离出钙 单个细胞内钙激活的钾电流。第三 目的是分析钙激活细胞的动力学行为。 钾通道，并表征钙离子和电压- 敏感度。因为这股洋流的运动行为 与毛细胞的特征频率相关 如果被调谐，它被认为在频率上起着主要作用 选择性。同时连接电池的单通道和全通道 细胞记录将用来比较单人的行为 钙离子通道与宏观钙激活钾 电流。 拟议的研究将分析这些离子流，以评估 毛细胞的调谐是否由基侧离子电导引起 与通过以下方式作用的机制共存或由其增强 睫状束中的转导过程。离子流 在电压钳位下测量将用于重建 在电流钳中可以看到膜共振。

The goal of the proposed research is to characterize the cellular mechanisms that contribute to tuning in turtle cochlear hair cells. By understanding how these cellular mechanisms contribute to frequency selectivity, we will be able to assess their limitations and applicability to hearing in higher vertebrates including man. A combination of whole-cell and single-channel patch-clamp techniques will be used on solitary cells isolated from identified regions of the turtle cochlea. The first aim is to analyze the mechanical response of the hair-cell ciliary bundle, and to determine the role of this response in the overall transduction mechanism. The source, strength and voltage-sensitivity of the ciliary motion will be determined. The ability of the transducer channel to detect this motion will be ascertained, and any variation in the size and voltage-sensitivity with characteristic frequency will be assessed. The second aim is to characterize further the conductances in the basolateral hair-cell membrane implicated in electrical resonance. Changes in the size and kinetics of the membrane currents in cells of known characteristic frequency will be analyzed using intracellular perfusion. Specific protocols address the isolation inward currents due to the apical transducer and the basolateral calcium current, the characterization of possible electrogenic transport of calcium out of the cell, and a separation of the calcium from the calcium-activated potassium currents in a single cell. The third aim is to analyze the kinetic behavior of the calcium-activated potassium channel and to characterize the calcium- and voltage- sensitivity. Since the kinetic behavior of this current is highly correlated with the characteristic frequency to which a hair cell is tuned, it is presumed to play a major role in frequency selectivity. Simultaneous cell-attached single-channel and whole- cell recording will be used to compare the behavior of the single channel and the macroscopic calcium-activated potassium current. The proposed research will analyze these ionic currents to assess whether hair-cell tuning due to basolateral ionic conductances coexists with, or is enhanced by, mechanisms acting via the transduction process in the ciliary bundle. The ionic currents measured under voltage-clamp will be used to reconstruct the membrane resonance seen in current-clamp.