Scheme for testing locomotor responses to cocaine.

Rat locomotor experiments were carried out in four distinct phases. Phase 1, “Acclimation", consisted of 3 consecutive days of 45-min in the test chamber with no interventions. Phase 2, “Training", involved 9 days of 90 min in the chamber with an i.p. injection of saline (S) or cocaine, 10 mg/kg C) at the 45-min time point. Phase 3, “No Drug", involved 15 “rest days" in the home cage with no interventions. Phase 4, “Challenge", was 2 days in the chamber with i.p. saline or cocaine at the respective 45-min time points.