Dual Mechanism for Bitter Avoidance in Drosophila
Dual Mechanism for Bitter Avoidance in Drosophila
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DOI：
10.1523/jneurosci.1312-14.2015
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发表时间：
2015-03-04
影响因子：
5.3
通讯作者：
Marion-Poll, Frederic
中科院分区：
文献类型：
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作者：
French, Alice Sarah;Sellier, Marie-Jeanne;Marion-Poll, Frederic
在苍蝇和人类中，苦味化学物质已知会抑制糖的检测，但这种抑制的适应性作用往往被忽视。最好的情况下，这种抑制被描述为有助于拒绝潜在的有毒食物，但没有研究已经解决了直接途径的相对重要性，涉及激活对糖敏感的细胞与间接途径代表的糖检测抑制。使用毒素来选择性地消融或破坏对糖敏感的细胞群体，我们评估了苍蝇对蔗糖与士的宁（其激活对糖敏感的细胞并抑制糖检测）或L-刀豆氨酸（其仅激活对糖敏感的细胞）混合的行为反应。正如预期的那样，在三种不同的摄食试验（长鼻延伸反应、毛细血管摄食和两种选择试验）中，具有消融的对乙酰氨基酚敏感细胞的果蝇未能检测到与蔗糖混合的L-刀豆氨酸。然而，这些苍蝇仍然能够避免士的宁与蔗糖混合。通过电生理学记录，我们确定了苦味分子在抑制蔗糖检测的效力上不同，并且糖感抑制作用影响长鼻和腿上的味觉细胞。士的宁不降低糖敏感细胞的光遗传学反应，从而表明这种抑制与糖转导直接相关。我们假设，糖敏感抑制代表了昆虫的一种机制，以防止摄入有害物质的混合物中发生。
In flies and humans, bitter chemicals are known to inhibit sugar detection, but the adaptive role of this inhibition is often overlooked. At best, this inhibition is described as contributing to the rejection of potentially toxic food, but no studies have addressed the relative importance of the direct pathway that involves activating bitter-sensitive cells versus the indirect pathway represented by the inhibition of sugar detection. Using toxins to selectively ablate or inactivate populations of bitter-sensitive cells, we assessed the behavioral responses of flies to sucrose mixed with strychnine (which activates bitter-sensitive cells and inhibits sugar detection) or with L-canavanine (which only activates bitter-sensitive cells). As expected, flies with ablated bitter-sensitive cells failed to detect L-canavanine mixed with sucrose in three different feeding assays (proboscis extension responses, capillary feeding, and two-choice assays). However, such flies were still able to avoid strychnine mixed with sucrose. By means of electrophysiological recordings, we established that bitter molecules differ in their potency to inhibit sucrose detection and that sugar-sensing inhibition affects taste cells on the proboscis and the legs. The optogenetic response of sugar-sensitive cells was not reduced by strychnine, thus suggesting that this inhibition is linked directly to sugar transduction. We postulate that sugar-sensing inhibition represents a mechanism in insects to prevent ingesting harmful substances occurring within mixtures.