Following home cage drinking, operant training began. Operant conditioning chambers (Medical Associates Inc., St. Albans, VT) were located in a different room from where the rats were housed. Chambers were contained within ventilated sound-attenuating cubicles, and comprised of a clear Plexiglas ceiling, front door and back wall, paneled aluminum side walls and a stainless steel bar floor. The right wall featured a central port containing a circular fluid receptacle, into which ethanol was delivered via a 20 ml syringe attached to a pump located outside the sound-attenuating cubicle. Chambers were outfitted with retractable levers flanking the port and a white chamber light (28 V, 100 mA) located centrally near the ceiling on the left wall. Responses on one lever (active lever) resulted in delivery of 0.1 ml of 20% EtOH and responses on the other, inactive, lever resulted in no programmed events. No explicit cues were used at any time during the conditioning sessions. To facilitate acquisition of the lever-press response, rats were placed overnight (12–14 hours) in the operant chambers for two nights in a row and allowed to
