Rats were given a minimum of 2 days habituation to the facility post-transport before surgery. The surgical procedure was performed as described previously 53 (link), using flat skull stereotaxic coordinates obtained from a brain atlas 90 . Briefly, rats were anesthetized with ketamine/xylazine (80–100mg/kg and 2–12mg/kg; i.p., respectively) and placed in a stereotaxic frame (Kopf Instrumentation; Tujunga, CA, USA). Deltaphase isothermal pads (Braintree Scientific, Braintree, MA, USA) were used to maintain body temperature. Bupivicaine was injected just under the skin and the skull was exposed to reveal bregma and lambda in order to level and drill the holes for electrode placement. For the electrochemical experiments, a combination bipolar stimulating electrode/infusion cannula (Plastics One, Roanoke, VA, USA) was placed above the posterior VTA (−5.9 AP, +0.8 ML, −8.8–9.0 DV). A guide cannula (Bioanalytical Systems, West Lafayette, IN, USA) for recording electrodes was positioned 2.5 mm deep into the brain over the shell subregion of the NAc (+1.2 AP, +0.8 ML). Reference electrodes were Ag/AgCl, and placed superficially in the contralateral cortex. For behavioral experiments, stainless steel guide cannulae (26 gauge, Plastics One) were bilaterally aimed at the VTA (−5.9 AP, +1.7 ML, −6.6 DV, relative to bregma) with a 10 degree angle.