Animals were trained to self-administer alcohol or water orally in a concurrent, two-lever, free-choice contingency. A continuous reinforcement (fixed ratio-1, FR1) schedule of reinforcement was used in which each lever press was reinforced. Animals acquired alcohol self-administration using a variation of the previously described saccharin fading free-choice operant conditioning protocol (Samson, 1986). The modified procedure in the present study utilized a sweetened solution containing 3% glucose and 0.125% saccharin (Sigma, St. Louis, MO) instead of water restriction and 0.2% saccharin to initiate and maintain operant responding (Funk et al., 2006). Animals respond for the sweetened solution within 1-2 training sessions, thereby circumventing the need for water restriction to initiate lever-pressing. Operant sessions during training were conducted 5 days per week between 09.00 h and 15.00 h (lights on at 06.00 h). Operant sessions were 30 min in duration, except during the initial days of training in which sessions lasted up to 2 h to permit acquisition of responding for the sweetened solution. Alcohol (ethanol, 10% w/v) then was added to the sweetened solution, and once mean responding stabilized (around 1
