Janes Tara A, Xu Fenglian, Syed Naweed I
Department of Cell Biology and Anatomy and the Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, 3280 Hospital Dr N.W., Calgary, AB, Canada, T2N4Z6.
Eur J Neurosci. 2015 Jul;42(2):1858-71. doi: 10.1111/ejn.12940. Epub 2015 Jun 12.
Respiratory behaviour relies critically upon sensory feedback from peripheral oxygen chemoreceptors. During environmental or systemic hypoxia, chemoreceptor input modulates respiratory central pattern generator activity to produce reflex-based increases in respiration and also shapes respiratory plasticity over longer timescales. The best-studied oxygen chemoreceptors are undoubtedly the mammalian carotid bodies; however, questions remain regarding this complex organ's role in shaping respiration in response to varying oxygen levels. Furthermore, many taxa possess distinct oxygen chemoreceptors located within the lungs, airways and cardiovasculature, but the functional advantage of multiple chemoreceptor sites is unclear. In this study, it is demonstrated that a distributed network of peripheral oxygen chemoreceptors exists in Lymnaea stagnalis and significantly modulates aerial respiration. Specifically, Lymnaea breath frequency and duration represent parameters that are shaped by interactions between hypoxic severity and its time-course. Using a combination of behaviour and electrophysiology approaches, the chemosensory pathways underlying hypoxia-induced changes in breath frequency/duration were explored. The current findings demonstrate that breath frequency is uniquely modulated by the known osphradial ganglion oxygen chemoreceptors during moderate hypoxia, while a newly discovered area of pneumostome oxygen chemoreception serves a similar function specifically during more severe hypoxia. Together, these findings suggest that multiple oxygen chemosensory sites, each with their own sensory and modulatory properties, act synergistically to form a functionally distributed network that dynamically shapes respiration in response to changing systemic or environmental oxygen levels. These distributed networks may represent an evolutionarily conserved strategy vis-à-vis respiratory adaptability and have significant implications for the understanding of fundamental respiratory control systems.
呼吸行为严重依赖于外周氧化学感受器的感觉反馈。在环境性或全身性缺氧期间，化学感受器的输入会调节呼吸中枢模式发生器的活动，以产生基于反射的呼吸增加，并且在更长的时间尺度上塑造呼吸可塑性。研究得最透彻的氧化学感受器无疑是哺乳动物的颈动脉体；然而，关于这个复杂器官在响应不同氧水平时对呼吸形成的作用，仍存在疑问。此外，许多生物类群在肺、气道和心血管系统中拥有独特的氧化学感受器，但多个化学感受器位点的功能优势尚不清楚。在本研究中，证明了椎实螺存在一个外周氧化学感受器的分布式网络，并且该网络显著调节空气呼吸。具体而言，椎实螺的呼吸频率和持续时间代表了由缺氧严重程度及其时间进程之间的相互作用所塑造的参数。使用行为学和电生理学方法相结合的方式，探索了缺氧诱导的呼吸频率/持续时间变化背后的化学感受通路。目前的研究结果表明，在中度缺氧期间，呼吸频率由已知的嗅检器神经节氧化学感受器独特地调节而出，而新发现的气门氧化学感受区域在更严重的缺氧期间发挥类似的功能。总之，这些发现表明，多个氧化学感受位点，每个位点都有其自身的感觉和调节特性，协同作用形成一个功能分布式网络，以响应不断变化的全身或环境氧水平动态地塑造呼吸。这些分布式网络可能代表了一种在呼吸适应性方面进化保守的策略，并且对于理解基本的呼吸控制系统具有重要意义。
