2.3 Apparatus

During the Alcohol Self-administration phase, volumetric drinking tubes (400 ml capacity) were used to monitor liquids consumption. Training, extinction and reinstatement sessions were conducted in standard operant conditioning chambers (Med Associates™) placed inside sound attenuating boxes with an exhauster that provided air circulation. Each chamber was equipped with a drinking reservoir (volume capacity 0.30 ml) positioned 4 cm above the grid floor in the center of the front panel of the chamber. Two retractable levers were located 3 cm to the right or to the left of the drinking receptacle. An infusion pump was activated only by responses on the right (active) lever, while responses on the left (inactive) lever were recorded but did not result in the activation of the pump. Auditory and visual stimuli were presented via a speaker and a light located on the front panel. The floor was a stainless steel grid, under which a tray was always filled with wood shavings (bedding). A microcomputer with software and interface manufactured by Med Associates™ controlled the operation of the boxes and the recording of the behavioral data. To produce the olfactory (odor) stimuli used in training and reinstatement sessions, five drops (approximately 0.1 ml) of orange or anise extract were placed in the bedding before the beginning of sessions.