AUTHOR=Mandel Samantha J. , Shoaf Madison L. , Braco Jason T. , Silver Wayne L. , Johnson Erik C. 

TITLE=Behavioral Aversion to AITC Requires Both Painless and dTRPA1 in Drosophila

JOURNAL=Frontiers in Neural Circuits

VOLUME=12

YEAR=2018

URL=https://www.frontiersin.org/journals/neural-circuits/articles/10.3389/fncir.2018.00045

DOI=10.3389/fncir.2018.00045

ISSN=1662-5110

ABSTRACT=<p>There has been disagreement over the functional roles of the <italic>painless</italic> gene product in the detection and subsequent behavioral aversion to the active ingredient in wasabi, allyl isothiocyanate (AITC). Originally, <italic>painless</italic> was reported to eliminate the behavioral aversion to AITC, although subsequent reports suggested that another trpA homolog, <italic>dTRPA1</italic>, was responsible for AITC aversion. We re-evaluated the role of the <italic>painless</italic> gene in the detection of AITC, employing several different behavioral assays. Using the proboscis extension reflex (PER) assay, we observed that AITC did not reduce PER frequencies in <italic>painless</italic> or <italic>dTRPA1</italic> mutants but did in wild-type genotypes. Quantification of food intake showed a significant decline in food consumption in the presence of AITC in wild-type, but not <italic>painless</italic> mutants. We adapted an oviposition choice assay and found wild-type oviposit on substrates lacking AITC, in contrast to <italic>painless</italic> and <italic>dTRPA1</italic> mutants. Lastly, tracking individual flies relative to a point source of AITC, showed a consistent clustering of wild-type animals away from the point source, which was absent in <italic>painless</italic> mutants. We evaluated expression patterns of both <italic>dTRPA1</italic> and <italic>painless</italic>, which showed expression in distinct central and peripheral populations. We identified the transmitter phenotypes of subsets of <italic>painless</italic> and <italic>dTRPA1</italic> neurons and found similar neuropeptides as those expressed by mammalian trpA expressing neurons. Using a calcium reporter, we observed AITC-evoked responses in both <italic>painless</italic> and <italic>dTRPA1</italic> expressing neurons. Collectively, these results reaffirm the necessity of <italic>painless</italic> in nociceptive behaviors and suggest experiments to further resolve the molecular basis of aversion.</p>