College of Agro-Biological Resource Sciences, School of Life and Environmental Sciences, University of Tsukuba, 1-1-1, Tennodai, Tsukuba, Ibaraki 305-8572, Japan.
Biomedical Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1, Higashi, Tsukuba, Ibaraki 305-8566, Japan.
Neurosci Lett. 2022 Jan 23;770:136384. doi: 10.1016/j.neulet.2021.136384. Epub 2021 Dec 7.
Ultraviolet light is quite toxic to all the animals and evoke the avoidance behavior of UV. The soil nematode Caenorhabditis elegans senses UV and is known to avoid UV by using four sensory neurons. However, it is not clear what signaling molecules act for UV avoidance in the neuronal pathway constituted of four sensory neurons. In addition, it is not clear whether this harmful environmental signal can be associated with other benefit signals such as food. In this study, by using newly developed assay system, we found that C. elegans can associate UV and food and changes behavioral strategy against harmful UV signal. This is the first indication that C. elegans shows associate learning with UV and food. Using our assay system, we also found that glutamate is used as a transmitter in both the UV avoidance and UV associate learning neural circuits. However, one sensory neuron showed a significant role for associative learning, compared to a complimentary role in four sensory neurons for direct associative learning, and different sets of glutamate receptors seemed to be acting for UV avoidance and UV associate learning. These findings suggest that a distinct neuronal network is used for UV learning compared to that for direct avoidance behavior of UV.
紫外线对所有动物都有很强的毒性，并能引起动物的避紫外行为。土壤线虫秀丽隐杆线虫能感知紫外线，并通过使用四个感觉神经元来避免紫外线。然而，目前尚不清楚在由四个感觉神经元组成的神经元通路中，哪些信号分子可以用于紫外线的回避。此外，也不清楚这种有害的环境信号是否可以与其他有益的信号（如食物）相关联。在这项研究中，我们通过使用新开发的测定系统，发现秀丽隐杆线虫可以将紫外线和食物联系起来，并改变针对有害紫外线信号的行为策略。这是秀丽隐杆线虫对紫外线和食物表现出联想学习的第一个迹象。利用我们的测定系统，我们还发现谷氨酸在紫外线回避和紫外线联想学习的神经回路中都被用作递质。然而，与四个感觉神经元在直接联想学习中的互补作用相比，一个感觉神经元在联想学习中表现出显著的作用，而且似乎有不同的谷氨酸受体集分别用于紫外线回避和紫外线联想学习。这些发现表明，与直接避免紫外线的行为相比，用于紫外线学习的神经元网络是不同的。
