DEVELOPMENT OF FUNCTIONAL CALCIUM CHANNELS IN CULTURED AVIAN PHOTORECEPTORS
DEVELOPMENT OF FUNCTIONAL CALCIUM CHANNELS IN CULTURED AVIAN PHOTORECEPTORS
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DOI：
10.1017/s0952523800005058
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发表时间：
1992-04-01
影响因子：
1.9
通讯作者：
WILSON, M
中科院分区：
文献类型：
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作者：
GLEASON, E;MOBBS, P;WILSON, M
脊椎动物的光感受器是一种特殊的神经元，因为它们能够持续释放钙介导的神经递质(Trifonov，1968；Hagins等人，1970)。在这项研究中，我们研究了胚胎第8天培养的鸡视锥细胞钙电流的发育和特征。视锥细胞的凝集素结合特性、视紫红质样免疫反应和油滴的存在来鉴定视锥细胞。使用全细胞膜片钳方法，我们在这些细胞培养三天后，略早于突触的出现，观察到了钙电流(Gleason&Wilson，1989)。由于锥体钙电流被镉和硝苯地平阻断，但被Bay K8644增强，它们最接近于L型电流(Nowycky等人，1985)。这些电流的一个意想不到的特征是，它们的门控范围在不同细胞之间变化很大，因此一些细胞的激活范围在-70 mV，而另一些细胞的激活范围为-25 mV。通过Fura-2负载细胞的钙离子成像来确定钙电流发展的时间进程，并描述细胞内钙的分布。正如预期的那样，年轻细胞的去极化未能增加胞浆钙，但在较老的细胞中，通常可以观察到三到四倍的增加。无论是静息状态还是去极化状态，大多数锥体细胞内钙离子浓度都存在区域性差异。在最成熟的圆锥体中，去极化使细胞末端的胞浆钙显著升高，而在油滴和椭球区周围的变化较小，表明钙通道定位于细胞的末端。
Vertebrate photoreceptors are unusual neurons in that they are capable of continuous calcium-mediated release of neurotransmitter (Trifonov, 1968; Hagins et al., 1970). In this study, we have examined the development and characteristics of calcium currents in chick cone cells placed in culture on embryonic day 8. Cone cells were identified by their lectin-binding properties, rhodopsin-like immunoreactivity, and the presence of an oil droplet. Using the whole-cell patch-clamp method, we have seen calcium currents in these cells after three days in culture, slightly before the appearance of synapses (Gleason & Wilson, 1989). Because cone calcium currents are blocked by cadmium and nifedipine but are enhanced by Bay K 8644, they most closely resemble L-type current (Nowycky et al., 1985). An unexpected feature of these currents is that their gating ranges varied widely between cells so that some cells showed the foot of their activation range at -70 mV and others as positive as -25 mV. Calcium imaging of fura-2 loaded cells was used to confirm the time course of calcium current development and describe the distribution of cytosolic calcium. As expected, depolarization of young cells failed to increase cytosolic calcium but in older cells an increase of threefold to fourfold was usually observed. Both at rest and during depolarization, most cone cells showed regional differences in internal calcium concentration. In the most mature cones, depolarization strongly elevated cytosolic calcium at the terminal end of the cell while producing a lesser change around the oil droplet and the ellipsoid region, suggesting that calcium channels are localized to the terminal.