there exists a complex interplay between the sensory and central effects of ethanol (Patel et al., 2004). A relationship between the smell of ethanol and its behavioral effects may also exist in insects. In the honeybee, ingestion of ethanol can impair olfactory learning and discrimination (Mustard et al., 2008). In Drosophila, ethanol is attractive at low concentrations, influences neural activity in olfactory neurons, and evokes locomotor activity (Hallem and Carlson, 2006; Kim et al., 1998; Wolf et al., 2002). Moreover, Drosophila lines selected for ethanol sedation resistance exhibit reduced attraction to ethanol (Hoffmann and Cohan, 1987). Here, we showed that ethanol exposure causes a strong down-regulation of specific olfactory genes, suggesting that olfactory responses to this ethologically relevant odor are modified at the level of gene expression. Whether ethanol elicits this response directly in the olfactory receptor neurons, or indirectly through olfactory transduction circuits or at other sites remains to be explored. Additionally, we found that, when 1 of the down-regulated genes, the olfactory co-receptor encoding Or83b, was ablated, the increase in ethanol-induced hyperactivity upon a second exposure was magnified. Most simply, these data indicate that olfaction in Drosophila regulates plasticity in the behavioral response to ethanol.
