Locomotor response to saline or cocaine injections. The same methods, apparatus and dependent measures were used with the exception that the activity chambers were not subdivided into peripheral and central zones. On successive test days, mice were injected (i.p.) with isotonic saline (10 ml/kg) or cocaine (10 mg/kg in isotonic saline at a volume of 10 ml/kg) and immediately placed in the activity chambers. An additional measure of cocaine sensitization was calculated by subtracting total distance traveled after the first cocaine injection from total distance traveled after the second cocaine exposure. Positive values indicated sensitization.
