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不同氣味劑分子已知能夠同時(shí)激發(fā)幾個(gè)不同類別的嗅覺(jué)神經(jīng)元，說(shuō)明存在一個(gè)組合編碼。 通過(guò)進(jìn)行一項(xiàng)新的行為測(cè)定，并用最先進(jìn)的方法對(duì)果蠅的特定神經(jīng)元進(jìn)行基因控制，Julia Semmelhack和 Jing Wang發(fā)現(xiàn)，低濃度引誘劑的吸引力完全依賴于一兩個(gè)神經(jīng)元中心或嗅小球。他們所采用的引誘劑為蘋(píng)果醋，用來(lái)指示果蠅喜歡的食物源——腐爛的水果。在低濃度時(shí)，蘋(píng)果醋觸發(fā)了6個(gè)嗅小球，并對(duì)果蠅有一種強(qiáng)烈的自然吸引力。當(dāng)6個(gè)嗅小球中的2個(gè)（DMA1 和 VA2）通過(guò)基因手段“關(guān)掉”時(shí)，吸引力被大大減小。嗅覺(jué)的一個(gè)共同特征是，大多數(shù)氣味隨著其強(qiáng)度增加會(huì)變得不太適宜，最終會(huì)變得討嫌。 這項(xiàng)研究揭示了該現(xiàn)象在神經(jīng)元層面上的一個(gè)可能的基礎(chǔ)，因?yàn)檩^高濃度的蘋(píng)果醋會(huì)激發(fā)更多的嗅小球，因而其吸引力會(huì)減小。 薦原始出處： 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. (責(zé)任編輯：Doctor001) |
