Operant Self-Administration of Alcohol in Rats

Rats were anesthetized with isoflurane (Henry Schein Medical) at a rate of 4% for induction and 2% for maintenance at an oxygen flow rate of 1 L/min. Surgery was conducted as previously described (Wright et al., 2017 (link)), with minor modifications. Vascular access buttons were connected to indwelling intravenous SILASTIC catheters (Instech Laboratories), which were inserted into the right jugular vein. Catheters were flushed twice daily with 0.1 ml heparinized saline (50 U/ml; Alfa Aesar) and ampicillin (30 mg/ml; VWR). Rats were given a 3 d recovery period before operant self-administration testing. Catheter patency was tested by intravenously administering 0.05 ml of xylazine (2.5 mg/ml) on days where rats were not exposed to alcohol or ketamine (Sunday) each week during the self-administration period. If rapid loss of muscle tone was not observed, the catheter was no longer considered patent, and a new catheter was inserted into the left jugular vein. If a rat failed a second patency test, the rat was removed from the study and not included in statistical analyses. We excluded some rats because of the failure of catheter patency (n = 2) during operant self-administration. The two excluded rats included one high-alcohol intake male that self-administered saline and one high-alcohol intake female that self-administered saline.