%0 Journal Article %A M. Paoli %A D. Münch %A A. Haase %A E. Skoulakis %A L. Turin %A C. G. Galizia %T Minute Impurities Contribute Significantly to Olfactory Receptor Ligand Studies: tales from Testing the Vibration Theory. %D 2017 %R 10.1523/ENEURO.0070-17.2017 %J eneuro %P ENEURO.0070-17.2017 %X Several studies have attempted to test the vibrational hypothesis of odorant receptor activation in behavioral and physiological studies using deuterated compounds as odorants. The results have been mixed. Here we attempted to test how deuterated compounds activate odorant receptors using calcium imaging of the fruit fly antennal lobe. We found specific activation of one area of the AL corresponding to inputs from a specific receptor. However, upon more detailed analysis, we discovered that an impurity of 0.0006% ethyl acetate in a chemical sample of benzaldehyde-d5 was entirely responsible for a sizable odorant-evoked response in Drosophila melanogaster olfactory receptor cells expressing dOr42b. Without gas chromatographic purification within the experimental setup, this impurity would have created a difference in the responses of deuterated and non-deuterated benzaldehyde, suggesting that dOr42b be a vibration sensitive receptor, which we show here not to be the case. Our results point to a broad problem in the literature on use of non GC-pure compounds to test receptor selectivity, and we suggest how the limitations can be overcome in future studies.Significance Statement How exactly odorant receptors create selectivity for some odorants against the vast number of alternatives remains as yet unclear, and is generally probed by measuring responses to different substances. Chemical senses are highly sensitive to minute amounts of odorants in the environment. Therefore, when testing the responses of olfactory receptors, substances of highest purity are used, generally 95% or 99%, i.e. with impurities of 5% or 1%. The authors report a case where an impurity of 0.0006% was sufficient to explain the full response of an olfactory receptor in a test situation. The authors demostrate why all experiments investigating the selectivity of odor receptors have to be performed with gas-chromatography-purified odors to eliminated potential impurity artifacts. %U https://www.eneuro.org/content/eneuro/early/2017/06/05/ENEURO.0070-17.2017.full.pdf