Department of Biology, Chungnam National University, Daejeon 34134, Korea.
Disease Target Structure Research Center, Korean Research Institute of Biosciences and Biotechnology, Daejeon 34141, Korea.
Int J Mol Sci. 2021 Jul 3;22(13):7191. doi: 10.3390/ijms22137191.
Olfaction is an important neural system for survival and fundamental behaviors such as predator avoidance, food finding, memory formation, reproduction, and social communication. However, the neural circuits and pathways associated with the olfactory system in various behaviors are not fully understood. Recent advances in optogenetics, high-resolution in vivo imaging, and reconstructions of neuronal circuits have created new opportunities to understand such neural circuits. Here, we generated a transgenic zebrafish to manipulate olfactory signal optically, expressing the Channelrhodopsin (ChR2) under the control of the olfactory specific promoter, . We observed light-induced neuronal activity of olfactory system in the transgenic fish by examining expression, and a calcium indicator suggesting that blue light stimulation caused activation of olfactory neurons in a non-invasive manner. To examine whether the photo-activation of olfactory sensory neurons affect behavior of zebrafish larvae, we devised a behavioral choice paradigm and tested how zebrafish larvae choose between two conflicting sensory cues, an aversive odor or the naturally preferred phototaxis. We found that when the conflicting cues (the preferred light and aversive odor) were presented together simultaneously, zebrafish larvae swam away from the aversive odor. However, the transgenic fish with photo-activation were insensitive to the aversive odor and exhibited olfactory desensitization upon optical stimulation of ChR2. These results show that an aversive olfactory stimulus can override phototaxis, and that olfaction is important in decision making in zebrafish. This new transgenic model will be useful for the analysis of olfaction related behaviors and for the dissection of underlying neural circuits.
嗅觉是一种重要的神经系统，对于生存和基本行为（如躲避捕食者、寻找食物、记忆形成、繁殖和社交交流）至关重要。然而，与各种行为中的嗅觉系统相关的神经回路和途径尚未完全了解。光遗传学、高分辨率体内成像和神经元回路重建的最新进展为理解这些神经回路创造了新的机会。在这里，我们生成了一种转基因斑马鱼，通过表达嗅觉特异性启动子控制下的 Channelrhodopsin（ChR2）来对嗅觉信号进行光学操纵。我们通过检查 表达和钙指示剂来观察转基因鱼中嗅觉系统的光诱导神经元活性，这表明蓝光刺激以非侵入性的方式激活了嗅觉神经元。为了研究光激活嗅觉感觉神经元是否会影响斑马鱼幼虫的行为，我们设计了一种行为选择范式，并测试了斑马鱼幼虫如何在两种相互冲突的感觉线索（厌恶气味或自然偏好的趋光性）之间进行选择。我们发现，当同时呈现相互冲突的线索（首选光和厌恶气味）时，斑马鱼幼虫会远离厌恶气味。然而，经过光激活的转基因鱼对厌恶气味不敏感，并且在 ChR2 的光刺激下表现出嗅觉脱敏。这些结果表明，厌恶的嗅觉刺激可以克服趋光性，并且嗅觉在斑马鱼的决策中很重要。这种新的转基因模型将有助于分析与嗅觉相关的行为，并剖析潜在的神经回路。
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