Cocaine self-administration, extinction and reinstatement

Rats were trained to press a lever to self-administer cocaine (0.5 mg/kg/inf) under a fixed-ratio (FR) 4 schedule of reinforcement during daily 2-h sessions. Once trained, rats underwent daily self-administration for 14 days prior to extinction training, during which the cocaine solution was replaced with saline. Each rat underwent extinction training until extinction criterion was met (<10 lever presses/2-h) at which point reinstatement testing was conducted. Procedures are described in detail in the supplemental information.