Ashmore J F, Meech R W
Nature. 1986;322(6077):368-71. doi: 10.1038/322368a0.
Mammalian hearing involves features not found in other species, for example, the separation of sound frequencies depends on an active control of the cochlear mechanics. The force-generating component in the cochlea is likely to be the outer hair cell (OHC), one of the two types of sensory cell through which current is gated by mechano-electrical transducer channels sited on the apical surface. Outer hair cells isolated in vitro have been shown to be motile and capable of generating forces at acoustic frequencies. The OHC membrane is not, however, electrically tuned, as found in lower vertebrates. Here we describe how the OHC resting potential is determined by a Ca2+-activated K+ conductance at the base of the cell. Two channel types with unitary sizes of 240 and 45 pS underlie this Ca2+-activated K+ conductance and we suggest that their activity is determined by a Ca2+ influx through the apical transducer channel, as demonstrated in other hair cells. This coupled system simultaneously explains the large OHC resting potentials observed in vivo and indicates how the current gated by the transducer may be maximized to generate the forces required in cochlear micromechanics.
哺乳动物的听觉具有其他物种所没有的特征，例如，声音频率的分离取决于对耳蜗力学的主动控制。耳蜗中产生力的成分可能是外毛细胞（OHC），它是两种感觉细胞之一，电流通过位于顶端表面的机械电换能通道进行门控。体外分离的外毛细胞已被证明具有运动能力，并能够在声频下产生力。然而，OHC膜并不像在低等脊椎动物中那样进行电调谐。在这里，我们描述了OHC静息电位是如何由细胞基部的Ca2+激活的K+电导决定的。两种单位尺寸分别为240和45 pS的通道类型构成了这种Ca2+激活的K+电导，我们认为它们的活性由通过顶端换能通道的Ca2+内流决定，正如在其他毛细胞中所证明的那样。这种耦合系统同时解释了在体内观察到的较大的OHC静息电位，并指出了换能器门控电流如何最大化以产生耳蜗微力学所需的力。
