Üçpunar Habibe K, Grunwald Kadow Ilona C
Department of Physiology, School of Medicine, Ankara Medipol University, Ankara, Turkey.
TUM School of Life Sciences, Technical University Munich, Freising, Germany.
Front Physiol. 2021 Apr 13;12:646401. doi: 10.3389/fphys.2021.646401. eCollection 2021.
CO differs from most other odors by being ubiquitously present in the air animals inhale. CO levels of the atmosphere, however, are subject to change. Depending on the landscape, temperature, and time of the year, CO levels can change even on shortest time scales. In addition, since the 18th century the CO baseline keeps increasing due to the intensive fossil fuel usage. However, we do not know whether this change is significant for animals, and if yes whether and how animals adapt to this change. Most insects possess olfactory receptors to detect the gaseous molecule, and CO is one of the key odorants for insects such as the vinegar fly to find food sources and to warn con-specifics. So far, CO and its sensory system have been studied in the context of rotting fruit and other CO-emitting sources to investigate flies' response to significantly elevated levels of CO. However, it has not been addressed whether flies detect and potentially react to atmospheric levels of CO. By using behavioral experiments, here we show that flies can detect atmospheric CO concentrations and, if given the choice, prefer air with sub-atmospheric levels of the molecule. Blocking the synaptic release from CO receptor neurons abolishes this choice. Based on electrophysiological recordings, we hypothesize that CO receptors, similar to ambient temperature receptors, actively sample environmental CO concentrations close to atmospheric levels. Based on recent findings and our data, we hypothesize that Gr-dependent CO receptors do not primarily serve as a cue detector to find food sources or avoid danger, instead they function as sensors for preferred environmental conditions.
与大多数其他气味不同，一氧化碳在动物吸入的空气中普遍存在。然而，大气中的一氧化碳水平会发生变化。根据地形、温度和一年中的时间不同，一氧化碳水平即使在最短的时间尺度上也会改变。此外，自18世纪以来，由于大量使用化石燃料，一氧化碳的基线水平持续上升。然而，我们不知道这种变化对动物是否有显著影响，如果有，动物是否以及如何适应这种变化。大多数昆虫拥有嗅觉感受器来检测气态分子，一氧化碳是果蝇等昆虫寻找食物来源和警告同类的关键气味物质之一。到目前为止，一氧化碳及其感觉系统一直是在腐烂水果和其他一氧化碳排放源的背景下进行研究，以调查果蝇对显著升高的一氧化碳水平的反应。然而，果蝇是否能检测并可能对大气中的一氧化碳水平做出反应，这一点尚未得到研究。通过行为实验，我们在此表明果蝇能够检测大气中的一氧化碳浓度，并且如果可以选择的话，它们更喜欢含有低于大气水平该分子的空气。阻断一氧化碳受体神经元的突触释放会消除这种选择。基于电生理记录，我们推测，与环境温度受体类似，一氧化碳受体能主动采样接近大气水平的环境一氧化碳浓度。基于最近的研究发现和我们的数据，我们推测依赖味觉受体（Gr）的一氧化碳受体主要不是作为寻找食物来源或避免危险的线索探测器，相反，它们作为首选环境条件的传感器发挥作用。
