Figure 2. Conditioned Place-Preference of Group 2 Mice.

Mean ± SEM of CPP scores. Group 2 mice have been backcrossed to the C57 strain for 14 generations (F₁₄) and have a >99.9% C57-congenic background. (a) Wild-type control mice (cocaine: n = 7, saline: n = 8) show a robust CPP induced by 20 mg/kg cocaine. (b) DAT-CI littermates (cocaine: n = 8, saline: n = 8) failed to show CPP or CPA to 20 mg/kg cocaine. All statistics denoted by asterisks are two-way ANOVA comparisons of the time bias (CPP score) observed post-conditioning (open bars) relative to saline-conditioned control mice (***, p < 0.001). An a priori hypothesis test was conducted for the between group (2 and 3) comparison of the DAT-CI mice responses (‡, p < 0.05).