Mean baseline ethanol consumption measured during three sessions (20–22) showed the 20% ethanol self-administration group (0.96 ± 0.10 g/kg/30min, n=23) consumed significantly higher levels of ethanol compared to the 10% ethanol self-administration group (0.39 ± 0.10 g/kg/30min, n=10) (T test; p<0.001). Two-way ANOVA comparing the daily consumption (g/kg/30 min) of the 20% ethanol group compared to the 10% ethanol group revealed an overall main effect of group [F(1,810)=14.1, p<0.001], and an overall main effect of session [F(27, 810)=1.9, p<0.01], but there was no significant interaction (group × session) [F(27, 810)=0.7, n.s.]. Post hoc analysis found significant differences for all 28 baseline days (Figure 2A). The amount of ethanol self-administered in each group significantly correlated with BECs (20% ethanol intermittent: r2=0.6667, p<0.001, Figure 2B; 10% ethanol continuous: r2=0.4782, p<0.05, Figure 2C). Two animals were excluded from BEC analysis because their BEC was well below what would be expected for the amount of ethanol they pressed for, indicating that the animals were not drinking the full 0.1 ml at each reward presentation. Together these results show that SD rats will self-administer and voluntarily consume high amounts of ethanol that are comparable to other out-bred rats.
