French, A. S., Sellier, M.-J., Moutaz, A. A., Guigue, A., Chabaud, M.-A., Reeb, P. D., … Marion-Poll, F.


Institut National de la Recherche Agronomique, Unite Mixte de Recherche (UMR) Institut d’Ecologie et des Sciences de l’Environnement de Paris, F-78026 Versailles, France, 2 AgroParisTech, De ´partement Sciences de la Vie et Sante F-75231 Paris, France, 3
Universidad Nacional del Comahue, Facultad d Ciencias Agrarias, Departamento de Estadistica, RA-8303 Cinco Saltos, Argentina, Centre National de la Recherche Scientifique (CNRS),UMR5203,
Institut de Ge´nomique Fonctionnelle, F-34094 Montpellier, France, 5 Institut National de la Sante et de la Recherche Me dicale, U661, F-34094 Montpellier, France, 6mUniversite ´s de Montpellier 1 and 2,UMR5203, F-34094 Montpellier, France, and 7 CNRS, Unite ´ mixte de RecherchesUMR9191, Evolution, Genomes, Comportement, Ecologie F-91198 Gif-sur-Yvette, France.




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 behavioural 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.


… “BL was delivered by a light fiber from a 480 nm light source LED (CoolLED pE-100; Scientifica) illuminating the whole animal.”…

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pE-100: A range of compact, simple-to-use, single wavelength illumination systems for screening fluorescence.

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The Journal of Neuroscience

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