Figure 4.

Strain comparisons during the substitution procedure suggest that the MSG substitution did not alter the relative differences in ethanol drinking behavior between B6 and D2 mice. For mice undergoing the MSG-substitution procedure (A), B6 and D2 mice did not significantly diverge from one another until the procedure employed 75 mM MSG. Two-way ANOVA with strain and ethanol concentration as the main factors revealed a significant difference between strains but no effect of ethanol during both the 75 mM and 50 mM MSG periods (p < 0.001, A₁). Significant differences between strains remained during the MSG substitution (A₂, p < 0.001, 2-way ANOVA). During the sucrose-substitution procedure (B), ethanol intakes by B6 and D2 mice diverged significantly during the 10% sucrose period as ethanol concentrations were raised above 3% (B₁; 2-way ANOVA, p < 0.001 for the strain factor and for the ethanol concentration factor). The significant strain differences, but not the ethanol concentration effect, were also present during the 7.5% and 5% sucrose periods (p < 0.001, 2-way ANOVA). There was a significant interaction between factors during the sucrose fade-out (B₂, p < 0.01, strain and sucrose concentrations as main factors). Post hoc analysis of the strain factor used Bonferroni’s multiple comparison tests, *p < 0.05, **p < 0.01, ***p < 0.001.