Department of Biology, University of Ottawa, Canada. Electronic address: https://twitter.com/biologycountry.
Department of Biology, University of Ottawa, Canada; Brain and Mind Research Institute, University of Ottawa, Canada.
Comp Biochem Physiol A Mol Integr Physiol. 2022 Aug;270:111244. doi: 10.1016/j.cbpa.2022.111244. Epub 2022 May 23.
Vertebrates need oxygen to survive. The central nervous system has an especially high energy demand, so brain and retinal neurons quickly die in anoxia. But fish of the genus Carassius are exceptionally anoxia-tolerant: the crucian carp (C. carassius) can survive months without oxygen in ice-covered ponds, and the common goldfish (C. auratus) can withstand hours of anoxia at room temperature. These fish previously offered insights into anoxia tolerance in the brain, heart, and liver. Here, we advance Carassius spp. as models to study anoxia tolerance in the retina. Electroretinogram and evoked potential recordings show that crucian carp reversibly downregulate their visual systems in anoxia, probably to save ATP. Notably, Carassius suppress their visual systems nearly twice as much as anoxia-tolerant turtles, Trachemys and Chrysemys spp., which are often promoted as the champions of anoxia tolerance. We summarize what is known about anoxia tolerance in the goldfish and crucian carp retinas, including cellular pathways which may protect retinal neurons from excitotoxic cell death. We compare the Carassius retina with two relevant models: natural anoxia tolerance in the turtle brain, and ischemic preconditioning in the rat retina. All three models include mitochondria as oxygen sensors: mitochondria depolarize due to mitochondrial ATP-dependent K channels, possibly to trigger neuroprotective second messenger cascades. The Carassius retina is an accessible and inexpensive model, with over 70 fruitful years of history in vision research. As a model for anoxia tolerance, it may provide new insights into diseases of the eye (like diabetes, macular degeneration, and eye stroke).
脊椎动物需要氧气才能生存。中枢神经系统的能量需求特别高，因此大脑和视网膜神经元在缺氧时会迅速死亡。但是，鲤鱼属的鱼类对缺氧具有异常的耐受性：鲫鱼（C. carassius）可以在被冰覆盖的池塘中数月没有氧气而存活，而普通金鱼（C. auratus）可以在室温下耐受数小时的缺氧。这些鱼类之前为研究大脑、心脏和肝脏的缺氧耐受性提供了启示。在这里，我们将 Carassius spp. 作为研究视网膜缺氧耐受性的模型。视网膜电图和诱发电位记录表明，鲫鱼在缺氧时可逆地下调其视觉系统，可能是为了节省 ATP。值得注意的是，Carassius 抑制其视觉系统的程度几乎是缺氧耐受的龟类（Trachemys 和 Chrysemys spp.）的两倍，这些龟类通常被认为是缺氧耐受的冠军。我们总结了金鱼和鲫鱼视网膜缺氧耐受性的已知知识，包括可能保护视网膜神经元免受兴奋性细胞死亡的细胞途径。我们将 Carassius 视网膜与两个相关模型进行了比较：龟脑的自然缺氧耐受性和大鼠视网膜的缺血预处理。这三个模型都将线粒体作为氧气传感器：由于线粒体 ATP 依赖性 K 通道，线粒体去极化，可能会触发神经保护的第二信使级联反应。Carassius 视网膜是一种易于获取且价格低廉的模型，在视觉研究方面已有 70 多年的历史。作为缺氧耐受性的模型，它可能为眼部疾病（如糖尿病、黄斑变性和眼部中风）提供新的见解。
