Department of Otolaryngology, Stanford University School of Medicine, Stanford, CA 94305, USA.
Neuron. 2013 Nov 20;80(4):960-72. doi: 10.1016/j.neuron.2013.08.025.
Adaptation is a hallmark of hair cell mechanotransduction, extending the sensory hair bundle dynamic range while providing mechanical filtering of incoming sound. In hair cells responsive to low frequencies, two distinct adaptation mechanisms exist, a fast component of debatable origin and a slow myosin-based component. It is generally believed that Ca(2+) entry through mechano-electric transducer channels is required for both forms of adaptation. This study investigates the calcium dependence of adaptation in the mammalian auditory system. Recordings from rat cochlear hair cells demonstrate that altering Ca(2+) entry or internal Ca(2+) buffering has little effect on either adaptation kinetics or steady-state adaptation responses. Two additional findings include a voltage-dependent process and an extracellular Ca(2+) binding site, both modulating the resting open probability independent of adaptation. These data suggest that slow motor adaptation is negligible in mammalian auditory cells and that the remaining adaptation process is independent of calcium entry.
适应是毛细胞机械转导的一个标志，它扩展了感觉毛束的动态范围，同时对传入的声音进行机械滤波。在对低频有反应的毛细胞中，存在两种不同的适应机制，一种是起源有争议的快速成分，另一种是基于肌球蛋白的缓慢成分。人们普遍认为，机械-电换能通道中的 Ca(2+)内流是两种适应形式所必需的。本研究调查了哺乳动物听觉系统中适应的钙依赖性。来自大鼠耳蜗毛细胞的记录表明，改变 Ca(2+)内流或内部 Ca(2+)缓冲对适应动力学或稳态适应反应几乎没有影响。另外两个发现包括一个电压依赖性过程和一个细胞外 Ca(2+)结合位点，它们都独立于适应调节静息开放概率。这些数据表明，哺乳动物听觉细胞中的缓慢运动适应可以忽略不计，而剩余的适应过程与 Ca(2+)内流无关。
