Deep Brain Stimulation
Before surgery, animals were handled for 3 days to habituate them to the experimenter and the stimulation procedure. Using a stereotaxic frame, anesthetized animals (ketamine/xylazine 80/5 mg/kg, intraperitoneally) were implanted with electrodes (MS303-3-B-SPC, bipolar, twisted, 8 mm; Plastics One, Roanoke, VA) reaching the NAcb core (coordinates: 1.10 mm anterior, 1.45 mm lateral, and 4.65 mm ventral to bregma). After surgery, animals were individually caged, and received buprenorphine (0.1 mg/kg intraperitoneally) every 8 h over 3 days to minimize pain. Following 4–5 days of recovery, animals received high-frequency stimulations daily (130 Hz, 100 μA, 60 μs pulse width; A310 Accupulser and A365 Stimulus Isolator; World Precision Instruments, Berlin, Germany) for 1 h per day (NAcb-DBS). Control animals (NAcb-sham) were connected to the stimulator without current being applied. At the end of the experiments, localization of electrodes in the NAcb was confirmed on cresyl violet-stained coronal sections (see Figure 2b). Animals with misplaced electrodes were excluded from all data sets.