Food reinforcement

Commercially available two-lever operant chambers located within sound-attenuating, ventilated enclosures (Coulbourn Instruments, LLC, Whitehall, PA) were used for all food reinforcement experiments. Rats were trained to lever press for a food reward (45 mg pellet; Bio-Serv, Flemington, NJ). During the daily 1 h training sessions, rats could press either lever (both active) under an FR1 schedule and earn up to 50 food pellets. The response requirement was gradually increased to FR10 over a period of 10 d. Following food training, rats were implanted with bilateral guide cannulae aimed at the NAc for PFI3 or vehicle (n = 7/group) infusions as described above. Rats were tested for the response rate 30 min after the last microinjection.