INTRACELLULAR CALCIUM IN HAIR CELLS

长期目标是了解细胞机制， 听毛细胞的转导和频率选择性。 工作 将集中在细胞内钙离子的作用，特别是那些相关的 调节受体的电共振机制 许多低等脊椎动物毛细胞的潜能。 电 共振源于电压依赖性Ca 2+电流的相互作用， Ca 2+激活的K+电流。 然而，细胞机制， 决定了毛细胞的调谐特性， 在基底膜上的位置尚不清楚。 实验将 检查海龟和鳄鱼的单个毛细胞的属性 耳蜗采用膜片钳记录和成像的信号从Ca 2 +- 敏感染料 这一时期的具体目标是：（1）绘制 沿着沿着的毛细胞中的离子电流，测试细胞是否调谐 具有更多的电压依赖性Ca 2+通道， 激活K+通道;（2）表征单个细胞的大小和动力学 膜斑中的K+通道，并探讨其调节因素 如细胞内Ca ~（2+）和蛋白质磷酸化;（3）利用Ca ~（2+）敏感的 染料，以测量细胞内Ca 2+的代谢，其静息 浓度及其进入和挤出机制。 其余的 浓度随毛细胞的调谐频率而变化？ (4)通过 控制其细胞内浓度， 参与机械-电传导通道的适应 以及它与发束的主动运动的联系; 将寻求高毛细胞和短毛细胞之间的特性， 鳄鱼的耳蜗 所有这些实验都将涉及测量 通过用一种柔软的纤维代替它们来改变发束的力学， 已知的顺从。 从这些研究中获得的信息可能有助于深入了解 控制膜通道的表达和定位， 成为疾病中功能障碍的目标。 它也可能揭示一个严格的 对细胞内Ca 2+水平的需求用于通道调节， 毛细胞的功能。 细胞内Ca ~（2+）介导的机制 可能是所有毛细胞的共同点，包括哺乳动物的毛细胞。 耳蜗，它们可能是发生不可逆转损伤的部位 在听觉过度刺激或氨基糖苷类药物中毒期间 抗生素

The long-term objectives are to understand the cellular mechanisms of transduction and frequency selectivity in auditory hair cells. The work will focus on the roles of intracellular Ca2+, especially those pertinent to regulation of the electrical resonance mechanism that tunes the receptor potentials of hair cells in many lower vertebrates. The electrical resonance stems from the interplay of a voltage-dependent Ca2+ current and a Ca2+-activated K+ current. However, the cellular mechanism which dictates a hair cell's tuning characteristics according to the cell's location on the basilar membrane is not known. The experiments will examine the attributes of single hair cells of the turtle's and alligator's cochleas employing patch-clamp recording and imaging of signals from Ca2+- sensitive dyes. The specific aims during this period are: (1) to map the ionic currents in hair cells along the cochlea, testing whether cells tuned to higher frequencies have more voltage-dependent Ca2+ channels and faster activating K+ channels; (2) to characterize the size and kinetics of single K+ channels in membrane patches and explore their modulation by factors such as internal Ca2+ and protein phosphorylation; (3) using Ca2+-sensitive dyes, to measure the metabolism of intracellular Ca2+, its resting concentration and its entry and extrusion mechanisms. Does the resting concentration vary with the frequency of tuning of the hair cell? (4) by manipulating its intracellular concentration, to examine calcium's involvement in adaptation of the mechano-electrical transduction channels and its link to active motion of the hair bundle; differences in mechanical properties will be sought between tall and short hair cells of the alligator's cochlea. All such experiments will involve measuring the mechanics of the hair bundles by displacing them with a flexible fibre of known compliance. Information from these studies may lead to insights into the mechanisms controlling the expression and localization of membrane channels which may be a target for malfunction in disease. It may also reveal a stringent demand on the intracellular Ca2+ level for channel regulation and functioning of the hair cells. The mechanisms mediated by internal Ca2+ are probably common to all hair cells, including those in the mammalian cochlea, and they may be the sites at which irreversible damage occurs during acoustic over-stimulation or poisoning with aminoglycoside antibiotics.