Department of Biology, University of Ottawa, Ottawa, ON, Canada, K1N 6N5.
J Exp Biol. 2023 Apr 15;226(8). doi: 10.1242/jeb.245529. Epub 2023 Apr 25.
The study of breathing in fishes has featured prominently in Journal of Experimental Biology (JEB), particularly during the latter half of the past century. Indeed, many of the seminal discoveries in this important sub-field of comparative respiratory physiology were reported first in JEB. The period spanning 1960-1990 (the 'golden age of comparative respiratory physiology') witnessed intense innovation in the development of methods to study the control of breathing. Many of the guiding principles of piscine ventilatory control originated during this period, including our understanding of the dominance of O2 as the driver of ventilation in fish. However, a critical issue - the identity of the peripheral O2 chemoreceptors - remained unanswered until methods for cell isolation, culture and patch-clamp recording established that gill neuroepithelial cells (NECs) respond to hypoxia in vitro. Yet, the role of the NECs and other putative peripheral or central chemoreceptors in the control of ventilation in vivo remains poorly understood. Further progress will be driven by the implementation of genetic tools, most of which can be used in zebrafish (Danio rerio). These tools include CRISPR/Cas9 for selective gene knockout, and Tol2 systems for transgenesis, the latter of which enables optogenetic stimulation of cellular pathways, cellular ablation and in vivo cell-specific biosensing. Using these methods, the next period of discovery will see the identification of the peripheral sensory pathways that initiate ventilatory responses, and will elucidate the nature of their integration within the central nervous system and their link to the efferent motor neurons that control breathing.
鱼类呼吸研究在《实验生物学杂志》（JEB）中占据重要地位，尤其是在上世纪后半叶。事实上，比较呼吸生理学这一重要分支领域的许多开创性发现最初都是在 JEB 上报道的。从 1960 年到 1990 年（“比较呼吸生理学的黄金时代”）期间，呼吸控制的研究方法得到了极大的创新。许多鱼类通气控制的指导原则都起源于这一时期，包括我们对 O2 作为鱼类通气驱动力的理解。然而，一个关键问题——外周 O2 感受器的身份——直到细胞分离、培养和膜片钳记录方法的建立才得到解答，这些方法表明，鳃神经上皮细胞（NEC）在体外对低氧做出反应。然而，NEC 以及其他潜在的外周或中枢化学感受器在体内通气控制中的作用仍知之甚少。遗传工具的应用将推动进一步的研究进展，其中大多数工具都可以在斑马鱼（Danio rerio）中使用。这些工具包括用于选择性基因敲除的 CRISPR/Cas9，以及用于转基因的 Tol2 系统，后者可以实现细胞途径的光遗传学刺激、细胞消融以及体内特定细胞的生物传感。利用这些方法，下一阶段的发现将确定启动通气反应的外周感觉通路，并阐明其在中枢神经系统中的整合性质及其与控制呼吸的传出运动神经元的联系。
