The hair cell as a presynaptic terminal.
The hair cell as a presynaptic terminal.
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毛细胞作为突触前末端。
DOI：
10.1111/j.1749-6632.1991.tb36494.x
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发表时间：
1991
影响因子：
5.2
通讯作者：
Hudspeth,AJ
中科院分区：
文献类型：
--
作者：
Roberts,WM;Jacobs,RA;Hudspeth,AJ
毛细胞是内耳的感觉受体，是电生理学研究的极好对象，因为它以实验上易处理的上皮细胞形式表现出处理和传递电信号所需的神经元特征。毛细胞的紧凑形状，基本上是一个短的，光滑的圆柱体，一端有一束机械敏感的静纤毛，赋予它一个等电位的内部理想的电压钳位。因为它缺乏缠结轴突和树突的过程，单个的毛细胞很容易从感觉上皮分离。解离后，整个细胞表面没有胶质细胞，细胞外贴片电极可以接近。这些和其他形态学特征有助于详细分析机械电转导和随后的电事件，导致化学传递通过传入突触。在几个重要的方面，毛细胞类似于非尖峰神经元。因为它们不需要动作电位来长距离传输信号，所以它们可以自由地使用梯度电位来执行复杂的信号处理任务，这些任务涉及与受体电流和膜电容相互作用的离子通道。此外，毛细胞既制造又接收化学突触。与大多数神经元的情况相反，所有这些重要的细胞过程都可以使用细胞内和细胞外电压钳方法进行研究。在本文中，我们将集中在突触前机制。耳朵中的每个毛细胞与第八脑神经的一个或多个传入纤维进行突触接触。轴突内记录表明，传递是量子的，需要细胞外介质中的Ca ~（2+）。毛细胞的去极化增加了兴奋性神经递质的释放，可能是谷氨酸，而超极化减少了在没有刺激的情况下发生的稳定释放。与大多数其他化学突触一样，递质的释放显然是通过离散活动区的胞吐作用发生的，这可以通过其独特的形态特征来识别。在毛细胞中，这些包括常规化学突触的共同特征：分离密集染色的突触前膜和突触后膜的突触间隙，
The hair cell, the sensory receptor of the internal ear, is an excellent subject for electrophysiological studies because it manifests the neuronal characteristics needed to process and transmit electrical signals in the experimentally tractable form of an epithelial cell. The hair cell's compact shape, essentially that of a short, smooth cylinder with a bundle of mechanically sensitive stereocilia at one end, endows it with an isopotential interior ideal for voltage clamping. Because it lacks entangling axonal and dendritic processes, an individual hair cell is easily dissociated from the sensory epithelium. After dissociation, the entire cellular surface is free of glial vestments and is accessible to extracellular patch electrodes. These and other morphological features have facilitated detailed analyses of mechanoelectrical transduction and the subsequent electrical events leading to chemical transmission across afferent synapse~.'-~In several important respects, hair cells resemble nonspiking neurons. Because they do not need action potentials to transmit signals over long distances, they are free to use graded potentials to perform sophisticated signal-processing tasks involving ion channels that interact with the receptor current and the membrane capacitance. In addition, hair cells both make and receive chemical synapses. In contrast to the situation with most neurons, all of these important cellular processes can be studied using intracellular and extracellular voltage-clamp methods. In this paper we shall focus on presynaptic mechanisms. Each hair cell in the ear makes synaptic contacts onto one or more afferent fibers of the eighth cranial nerve. Intraaxonal recordings have shown that transmission is quanta1 and requires Ca2'in the extracellular medi~ m.~ Depolarization of the hair cell increases the release of an excitatory neurotransmitter, probably glutamate, and hyperpolarization diminishes the steady release that occurs in the absence of stimulation.'As at most other chemical synapses, transmitter release evidently occurs by exocytosis at discrete active zones, which can be recognized by their distinctive morphological features. In hair cells, these include the features common to conventional chemical synapses: a synaptic cleft separating densely stained pre-and postsynaptic membranes, and