Repeated aripiprazole treatment increased avoidance response disruption and sensitivity to aripiprazole re-exposure. Number of avoidance responses made by the rats from the three aripiprazole treatment groups (ARI 3.0, 10.0, and 30.0 mg/kg) and the vehicle group (VEH) on the last training (predrug) day and throughout the five drug test days (a), and on the aripiprazole (1.5 mg/kg) challenge test (b) are expressed as mean + standard error of the mean (SEM). *p<0.05, **p<0.01, ***p<0.001 relative to VEH group; #p<0.05 for comparison to the ARI 3.0 group.