A heroin self-administration paradigm was performed in adult male Long Evans rats (Charles River, Wilmington, MA) for two weeks as previously described.(26–28) This dosing paradigm does not induce physical dependence.(29) Animals were sacrificed either 1 hour or 24 hours after the last self-administration session by CO2 followed by decapitation, brains frozen and striata dissected using a 2mm micro-punch.
