Rapid tolerance is defined as a reduction in ethanol sensitivity during a second exposure to the drug following recovery from an earlier initial exposure (Devineni et al., 2011; Scholz, 2009). Control w1118 flies became sedated during both a first (E) and second (EE) ethanol exposure separated by four hours of recovery in ethanol sedation assays, but they were significantly less sensitive during the second challenge with ethanol (females, Figure 3A and C; males, Figure 3B and D). Ethanol sensitivity following an initial exposure to water (WE group) was not altered compared to flies with no prior ethanol experience (E group; Figure 3A–D), indicating that blunted ethanol sensitivity in EE flies is not due to a handling artifact and instead requires multiple exposures to the drug. Internal ethanol concentrations were indistinguishable during a first and second ethanol exposure (females, Figure 3E; males, Figure 3F). We conclude that the decreased ethanol sensitivity during the second ethanol exposure in ethanol sedation assays is due to altered pharmacodynamic properties of the drug and that this change in behavior represents the development of functional rapid
