Figure 2.

Concentration dependent effect. Preference assay for ethanol exposed flies fed with naltrexone (0–0.5% w/v) for 24 h before being starved for 24 h and tested for ethanol preference in the CAFE assay. Preference indices measured at 2 and 24 h. Columns represent three independent experiments, each consisting of three assay tubes containing 6–8 flies each. n = 9. Error bars are SEM. Statistical significance was measured by two-way ANOVA with Bonferroni multiple comparisons test. The effect of naltrexone treatment was overall highly significant p < 0.0001 but there was no statistical difference between consecutive naltrexone concentrations tested. The effect of time was not significant p = 0.175.