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Published May 15, 2007 | Supplemental Material
Journal Article Open

Light Activation of an Innate Olfactory Avoidance Response in Drosophila


How specific sensory stimuli evoke specific behaviors is a fundamental problem in neurobiology. In Drosophila, most odorants elicit attraction or avoidance depending on their concentration, as well as their identity [1]. Such odorants, moreover, typically activate combinations of glomeruli in the antennal lobe of the brain 2, 3 and 4, complicating the dissection of the circuits translating odor recognition into behavior. Carbon dioxide (CO_2), in contrast, elicits avoidance over a wide range of concentrations 5 and 6 and activates only a single glomerulus, V [5]. The V glomerulus receives projections from olfactory receptor neurons (ORNs) that coexpress two GPCRs, Gr21a and Gr63a, that together comprise a CO_2 receptor 7, 8 and 9. These CO_2-sensitive ORNs, located in the ab1 sensilla of the antenna, are called ab1c neurons [10]. Genetic silencing of ab1c neurons indicates that they are necessary for CO_2-avoidance behavior [5]. Whether activation of these neurons alone is sufficient to elicit this behavior, or whether CO_2 avoidance requires additional inputs (e.g., from the respiratory system), remains unclear. Here, we show that artificial stimulation of ab1c neurons with light (normally attractive to flies) elicits the avoidance behavior typical of CO_2. Thus, avoidance behavior appears hardwired into the olfactory circuitry that detects CO_2 in Drosophila.

Additional Information

© 2007 Elsevier Ltd. Under an Elsevier user license. Received: March 3, 2007; Revised: April 5, 2007; Accepted: April 11, 2007; Published online: May 10, 2007. We thank Martin Heisenberg for laboratory space, access to instrumentation facilities, and helpful discussions; Reinhard Wolf for advice; Hans Kaderschabeck for building T-maze prototypes; Allan Wong and Vivek Jayaraman for comments on the manuscript; and Richard Axel for advice and discussion. We also thank Elissa Hallem for the help with single-sensillum recordings and Zoltan Nadasdy for help with raster plots. This work was supported by the Alexander von Humboldt foundation (D.J.A.) and the National Science Foundation (S.B.). D.J.A. is an Investigator of the Howard Hughes Medical Institute.

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