Cholinergic control of membrane conductance and intracellular free Ca2+ in outer hair cells of the guinea pig cochlea
Cholinergic control of membrane conductance and intracellular free Ca2+ in outer hair cells of the guinea pig cochlea
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DOI：
10.1054/ceca.2000.0145
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发表时间：
2000-09-01
期刊：
影响因子：
4
通讯作者：
Mammano, F
中科院分区：
文献类型：
--
作者：
Evans, MG;Lagostena, L;Mammano, F
我们已经研究了胆碱能激动剂对外毛细胞的作用，无论是在原位和分离的豚鼠耳蜗，结合新的快速CCD技术的Ca 2+成像和传统的膜片钳方法。卡巴胆碱（1 mM）激活的电流具有接近-70 mV的反转电位和钟形I-V曲线，表明它是Ca 2+激活的K+电流。在少数细胞中，这种电流之前是一个短暂的内向电流，可能是由于Ca 2+和其他阳离子通过乙酰胆碱（ACh）受体流入。Ca 2+信号的幅度是最大的在一个有限的区域在基底极的细胞和急剧下降的顶端，兼容的Ca 2 +-流入和/或Ca 2 +-诱导的Ca 2 +-释放在细胞的基础。Ca 2 +-上升的时间过程是最快的在基地，但它仍然稍慢，更圆，比K+电流。在一些记录中，观察到K+电流，而细胞内Ca 2+没有任何可测量的变化。在大多数测试的细胞中，咖啡因（5 mM）增强（18%）K+电流，而兰尼碱（0.1 mM）降低（19%）。结果根据位于细胞底部的不稳定细胞内Ca 2+储存进行了讨论，靠近Ca 2+渗透性ACh受体通道和Ca 2+激活的K+通道，其对发生在该区域的Ca 2+升高的贡献通道是可变的，并且可能取决于其重新填充Ca 2+的能力。(C)2000年哈考特出版社有限公司
We have studied the action of cholinergic agonists on outer hair cells, both in situ and isolated from the cochlea of the guinea pig, combining new fast CCD technology for Ca2+ imaging and conventional patch-clamp methods. Carbachol (1 mM) activated a current with a reversal potential near -70 mV and a bell-shaped I-V curve, suggesting that it was a Ca2+-activated K+ current. In a few cells, this current was preceded by a transient inward current, probably owing to an influx of Ca2+ and other cations through the acetylcholine (ACh) receptors. The amplitude of the Ca2+ signal was maximal in a circumscribed region at the basal pole of the cell and decreased steeply towards the apical pole, compatible with Ca2+-influx and/or Ca2+-induced Ca2+-release at the cells base. The time course of the Ca2+-rise was fastest at the base, but it was still slightly slower, and more rounded, than that of the K+ current. In some recordings the K+ current was observed without any measurable change of intracellular Ca2+. The K+ current was potentiated (18%) by caffeine (5 mM), and decreased (19%) by ryanodine (0.1 mM) in the majority of cells tested. The results are discussed in terms of a labile intracellular Ca2+ store located at the base of the cell, close to the Ca2+-permeable ACh receptor channels and Ca2+-activated K+ channels, whose contribution to the Ca2+ rise occurring in the region of the channels is variable, and probably dependent on its ability to refill with Ca2+. (C) 2000 Harcourt Publishers Ltd.