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不同气味剂分子已知能够同时激发几个不同类别的嗅觉神经元，说明存在一个组合编码。 通过进行一项新的行为测定，并用最先进的方法对果蝇的特定神经元进行基因控制，Julia Semmelhack和 Jing Wang发现，低浓度引诱剂的吸引力完全依赖于一两个神经元中心或嗅小球。他们所采用的引诱剂为苹果醋，用来指示果蝇喜欢的食物源——腐烂的水果。在低浓度时，苹果醋触发了6个嗅小球，并对果蝇有一种强烈的自然吸引力。当6个嗅小球中的2个（DMA1 和 VA2）通过基因手段“关掉”时，吸引力被大大减小。嗅觉的一个共同特征是，大多数气味随着其强度增加会变得不太适宜，最终会变得讨嫌。 这项研究揭示了该现象在神经元层面上的一个可能的基础，因为较高浓度的苹果醋会激发更多的嗅小球，因而其吸引力会减小。 荐原始出处： Nature 459, 218-223 (14 May 2009) | doi:10.1038/nature07983 Select Drosophila glomeruli mediate innate olfactory attraction and aversion Julia L. Semmelhack1 & Jing W. Wang1 1 Neurobiology Section, Division of Biological Sciences, University of California, San Diego, La Jolla, California 92093, USA Fruitflies show robust attraction to food odours, which usually excite several glomeruli. To understand how the representation of such odours leads to behaviour, we used genetic tools to dissect the contribution of each activated glomerulus. Apple cider vinegar triggers robust innate attraction at a relatively low concentration, which activates six glomeruli. By silencing individual glomeruli, here we show that the absence of activity in two glomeruli, DM1 and VA2, markedly reduces attraction. Conversely, when each of these two glomeruli was selectively activated, flies showed as robust an attraction to vinegar as wild-type flies. Notably, a higher concentration of vinegar excites an additional glomerulus and is less attractive to flies. We show that activation of the extra glomerulus is necessary and sufficient to mediate the behavioural switch. Together, these results indicate that individual glomeruli, rather than the entire pattern of active glomeruli, mediate innate behavioural output. (责任编辑：Doctor001) |
