果蝇能够本能地避开二氧化碳，比如说由紧张的其他果蝇所产生的二氧化碳，但当二氧化碳与其他气味剂（如由成熟的水果所产生的气味剂）相结合时，它们又能克服这种先天排斥力。

Stephanie Turner 和Anandasankar Ray报告说，这类能够改变行为的食物气味剂直接作用于果蝇触角中对二氧化碳敏感的神经元上，而不是像人们所想的那样通过其他嗅觉通道间接发挥作用。其他天然出现的气味剂也能阻断库蚊对二氧化碳有反应的神经元的作用。库蚊是西尼罗河病毒及丝虫病的昆虫媒介。鉴于这些昆虫能被人呼出的二氧化碳所吸引，这些抑制蚊子中对二氧化碳敏感的神经元的抑制剂，有可能帮助寻找通过阻断这一通道发挥作用的驱蚊剂。

原始出处：

Nature 461, 277-281 (10 September 2009) | doi:10.1038/nature08295

Modification of CO2 avoidance behaviour in Drosophila by inhibitory odorants

Stephanie Lynn Turner1 & Anandasankar Ray2

1 Cellular, Molecular, and Developmental Biology Program,
2 Department of Entomology, University of California, Riverside, California 92521, USA
Correspondence to: Anandasankar Ray2 Correspondence and requests for materials should be addressed to A.R.

The fruitfly Drosophila melanogaster exhibits a robust and innate olfactory-based avoidance behaviour to CO2, a component of odour emitted from stressed flies1. Specialized neurons in the antenna and a dedicated neuronal circuit in the higher olfactory system mediate CO2 detection and avoidance1, 2. However, fruitflies need to overcome this avoidance response in some environments that contain CO2 such as ripening fruits and fermenting yeast, which are essential food sources. Very little is known about the molecular and neuronal basis of this unique, context-dependent modification of innate olfactory avoidance behaviour. Here we identify a new class of odorants present in food that directly inhibit CO2-sensitive neurons in the antenna. Using an in vivo expression system we establish that the odorants act on the Gr21a/Gr63a CO2 receptor3. The presence of these odorants significantly and specifically reduces CO2-mediated avoidance behaviour, as well as avoidance mediated by 'Drosophila stress odour'. We propose a model in which behavioural avoidance to CO2 is directly influenced by inhibitory interactions of the novel odours with CO2 receptors. Furthermore, we observe differences in the temporal dynamics of inhibition: the effect of one of these odorants lasts several minutes beyond the initial exposure. Notably, animals that have been briefly pre-exposed to this odorant do not respond to the CO2 avoidance cue even after the odorant is no longer present. We also show that related odorants are effective inhibitors of the CO2 response in Culex mosquitoes that transmit West Nile fever and filariasis. Our findings have broader implications in highlighting the important role of inhibitory odorants in olfactory coding, and in their potential to disrupt CO2-mediated host-seeking behaviour in disease-carrying insects like mosquitoes.