CBL-GFRα1 double transgenic mice have an increased behavioral response to amphetamine. (a) Both double transgenic (DT) and non-transgenic littermate (wildtype, WT) controls show a normal increased activity level when initially placed in the chamber (activity levels at Time = 10 and 20 min were significantly greater than levels at Time = 40 min and all subsequent times; p < 0.001 two-way repeated measures ANOVA; p < 0.05, all pairwise multiple comparison post hoc analysis; WT, n = 9; DT, n = 6). There was no genotype effect. (b) Following administration of amphetamine, there is a much greater degree of behavioral activation in the DT group (p = 0.001 for comparison of factor ‘genotype’, ANOVA, n = 8 both groups) (VEH, vehicle; AMPH, amphetamine).