Zachar Peter C, Pan Wen, Jonz Michael G
Department of Biology, University of Ottawa, Ottawa, Ontario, Canada.
Department of Biology, University of Ottawa, Ottawa, Ontario, Canada
J Neurophysiol. 2017 Dec 1;118(6):3014-3023. doi: 10.1152/jn.00237.2017. Epub 2017 Sep 13.
The neuroepithelial cell (NEC) of the fish gill is an important model for O sensing in vertebrates; however, a complete picture of the chemosensory mechanisms in NECs is lacking, and O chemoreception in vertebrates that are tolerant to anoxia has not yet been explored. Using whole cell patch-clamp recording, we characterized four types of ion channels in NECs isolated from the anoxia-tolerant goldfish. A Ca-dependent K current () peaked at ~20 mV, was potentiated by increased intracellular Ca, and was reduced by 100 μM Cd A voltage-dependent inward current in Ba solution, with peak at 0 mV, confirmed the presence of Ca channels. A voltage-dependent K current () was inhibited by 20 mM tetraethylammonium and 5 mM 4-aminopyridine, revealing a background K current () with open rectification. Mean resting membrane potential of -45.2 ± 11.6 mV did not change upon administration of hypoxia (Po = 11 mmHg), nor were any of the K currents sensitive to changes in Po during whole cell recording. By contrast, when the membrane and cytosol were left undisturbed during fura-2 or FM 1-43 imaging experiments, hypoxia increased intracellular Ca concentration and initiated synaptic vesicle activity. 100 μM Cd and 50 μM nifedipine eliminated uptake of FM 1-43. We conclude that Ca influx via L-type Ca channels is correlated with vesicular activity during hypoxic stimulation. In addition, we suggest that expression of in gill NECs is species specific and, in goldfish, may contribute to an attenuated response to acute hypoxia. This study provides the first physiological characterization of oxygen chemoreceptors from an anoxia-tolerant vertebrate. Neuroepithelial cells (NECs) from the gills of goldfish displayed L-type Ca channels and three types of K channels, one of which was dependent upon intracellular Ca Although membrane currents were not inhibited by hypoxia during patch-clamp recording, this study is the first to show that NECs with an undisturbed cytosol responded to hypoxia with increased intracellular Ca and synaptic vesicle activity.
鱼类鳃部的神经上皮细胞（NEC）是脊椎动物中氧感知的重要模型；然而，NECs化学感应机制的全貌仍不明确，并且对耐缺氧脊椎动物的氧化学感受尚未进行探索。我们采用全细胞膜片钳记录技术，对从耐缺氧金鱼分离出的NECs中的四种离子通道进行了特性描述。一种钙依赖性钾电流（）在约20 mV时达到峰值，细胞内钙增加会使其增强，100 μM的镉可使其降低。在钡溶液中一种电压依赖性内向电流，在0 mV时达到峰值，证实了钙通道的存在。一种电压依赖性钾电流（）被20 mM四乙铵和5 mM 4-氨基吡啶抑制，揭示了一种具有开放整流特性的背景钾电流（）。平均静息膜电位为-45.2±11.6 mV，在给予低氧（Po = 11 mmHg）时未发生变化，并且在全细胞记录过程中，任何钾电流对Po的变化均不敏感。相比之下，在fura-2或FM 1-43成像实验中，当细胞膜和细胞质未受干扰时，低氧会增加细胞内钙浓度并引发突触小泡活动。100 μM的镉和50 μM的硝苯地平消除了FM 1-43的摄取。我们得出结论，在低氧刺激期间，通过L型钙通道的钙内流与小泡活动相关。此外，我们认为鳃NECs中 的表达具有物种特异性，在金鱼中，可能导致对急性低氧的反应减弱。本研究首次对耐缺氧脊椎动物的氧化学感受器进行了生理学特性描述。金鱼鳃部的神经上皮细胞（NECs）表现出L型钙通道和三种类型的钾通道，其中一种依赖于细胞内钙。尽管在膜片钳记录过程中膜电流未被低氧抑制，但本研究首次表明，细胞质未受干扰的NECs会对低氧做出反应，细胞内钙增加且突触小泡活动增强。
