CELLULAR BASIS OF TUNING IN THE COCHLEA

拟议研究的目标是表征细胞 这些机制有助于耳蜗的调谐。 使用 贴片电极和荧光成像技术的组合， 红耳猴的单个毛细胞和完整的基底乳头中 乌龟 Trachemys scripta elegans，我们将解决两个问题：（1） 如何表达的渠道，确定的特点， 频率沿着上皮的长度变化;以及（2） 由传出纤维和机械调制的共振质量 毛细胞的特性 在回答第一个问题时，我们将测试以下假设： 在较低频率的细胞是由于一个整体的电压依赖 钾电导：部分适应外向整流 电导（KV）和内向整流电导（KIR）。 此外，通过精确地将通道表达和 在完整上皮的特征频率，我们将在原位测试 预测的主要电流，伊卡和IK（Ca），以前牵连 在调谐更高频率的毛细胞在基础上的上皮细胞是 补充或替代IKV和IK（IR）的顶点。 额外 实验将测试通道表达的可塑性 海龟对不同的体温超过20摄氏度的范围。 针对第二个问题的实验检验了以下假设： 毛细胞共振的质量不仅受到 传出纤维，但毛细胞的机械性能以及。 将对完整上皮中的毛细胞进行电压钳实验。 用于解剖突触后电位的离子基础， 传出纤维的电刺激。 我们亦会探讨 传出活动的机制不仅是由 通过调节两个基底外侧毛细胞电导， 包括来自转导极附近的顶端突触的成分。 其中包括一些实验，探讨电压依赖性 通过转导通道检测海龟毛细胞的束运动 从而调节电谐振的质量。 最终 实验将使用共聚焦显微镜检查Ca 2-的作用， 作为传出和机械的共同细胞内效应器， 输入. 通过了解这些细胞机制如何决定频率 选择性，我们将能够评估其局限性和适用性 高等脊椎动物听觉的生理学和病理生理学， 包括人。

The goal of the proposed research is to characterize the cellular mechanisms that contribute to tuning in the cochlea. Using a combination of patch electrode and fluorescence imaging techniques on both solitary hair cells and in intact basilar papillae from the red-eared turtle. Trachemys scripta elegans, we will address two questions: (1) how does the expression of channels that determine the characteristic frequency vary along the length of the epithelium; and (2) how is the quality of resonance modulated by efferent fibers and mechanical properties of the hair cell? In answering the first question we will test the hypothesis that tuning in lower frequency cells is due to an ensemble of voltage-dependent potassium conductances: a partially-adapting outwardly-rectifying conductance (KV), and an inwardly-rectifying conductance (KIR). Furthermore, by precisely correlating channel expression and characteristic frequency in the intact epithelium, we will test in situ the prediction that the major currents, ICa and IK(Ca), previously implicated in tuning higher frequency hair cells at the base of the epithelium are supplemented or replaced by IKV and IK(IR) at the apex. Additional experiments will test the plasticity of channel expression by acclimating turtles to different body temperatures over a range of 20oC. The experiments addressing the second question test the hypothesis that the quality of hair cell resonance is modulated not only by the activity of efferent fibers, but by mechanical properties of the hair cell as well. Voltage-clamp experiments on hair cells in the intact epithelium will be used to dissect the ionic basis of post synaptic potentials produced by electrical stimulation of efferent fibers. We will also explore the hypothesis that the mechanism of efferent activity is mediated not only via modulation of two basolateral hair cell conductances, buy may also include a component from apical synapses near the transduction pole. Included are experiments that explore whether the voltage-dependent bundle motion of turtle hair cells is detected by transduction channels and thereby modulates the quality of electrical resonance. The final experiments will use confocal microscopy to examine the role of Ca2minus as a common intracellular effector for both efferent and mechanical input. By understanding how these cellular mechanisms determine frequency selectivity, we will be able to assess their limitations and applicability to the physiology and pathophysiology of hearing in higher vertebrates, including man.