Male C57/BL/6 mice 10–12 weeks old were obtained from Jackson Laboratory and housed on a 12-hour light-dark cycle with access to food and water ad libitum. Mice were injected i.p. with cocaine (20 mg/kg, Sigma) or saline once per day for 7 days. 24 hrs after the last dose, NAc was punch dissected from mice as described previously (Kumar et al., 2005).
