Animal Care and Surgical Techniques
All animal treatment was in accordance with National Institutes of Health guidelines for laboratory animal care, and all protocols were approved by the Medical University of South Carolina Institutional Animal Care and Use Committee. Male Sprague–Dawley rats (~350 g) were individually housed on a 12 h reverse light cycle and were food restricted (20 g chow per day). Catheters were surgically implanted into the right jugular vein (0.02 ID, 0.047 OD, Bio-sil). Prophylactic antibiotic (Timentin 10 mg/0.1 ml, i.v.) was administered during surgery and 3 days postoperatively. Catheters were flushed daily with heparin until the end of self-administration. Cannulae (26 gauge) were implanted into the NAc using the following coordinates: +1.5 A/P, +1.8 M/L, −5.5 D/V (Paxinos and Watson, 2005).