Behavioural data
To analyze the AMPH -induced psychomotor responses, a three-way ANOVA with the factors genotype, AMPH dose and time (for repeated measures) was used. To analyze the AMPH self-administration data, number of rewards were analyzed using a three-way ANOVA with the factor genotype, access type and self-administration session (for repeated measures). No outlier test was performed. Statistics were performed in IBM SPSS statistics version 23. Student’s t-test was conducted as post-hoc test when allowed.