Conditioned place preference in CN98 WT and mutant mice. Scores represent the difference in seconds between the post- and pre-conditioning time spent in the drug-associated compartment. Values represent mean ± SEM (n = 12–14). *P < 0.05, **P < 0.01, ***P < 0.001 vs. saline-treated mice of the same genotype (ANOVA followed by Fisher’s test).