Ventilation fan

Mice were tested in standard operant chambers configured with two retractable levers, a centrally located well for liquid reinforcers, house light, and a tone generator and stimulus light above the well. The chambers were situated in sound-attenuating cubicles with a ventilation fan (Med Associates, St. Albans, VT). One lever was assigned as the “active” lever, with responses resulting in access to ethanol or sucrose reinforcement paired with a light and tone stimulus (80 dB). Ethanol or sucrose reinforcement (20 ul) was delivered to the well by an infusion pump (activated for 2 sec). Responses on the ‘inactive lever” were recorded, but did not result in any stimulus consequences or reinforcement delivery. Stimulus events and responses were controlled and monitored using Med PC, Version IV software (Med Associates, Inc., St. Albans, VT). At the end of each session, any residual fluid left in the well was collected with a pipette, measured, and subtracted from the total volume of reinforcer delivered. The corrected volume was used to calculate g/kg ethanol or ml/kg sucrose intake during the sessions.

Mice were tested in standard operant conditioning chambers configured with 2 retractable levers, a centrally located well for liquid reinforcers, house light, a tone generator, and a stimulus light above the well. The chambers were situated in sound-attenuating cubicles with a ventilation fan (Med Associates; Fairfax, VT). One lever was assigned as the “active” lever, with scheduled responses activating an infusion pump that delivered alcohol (12% v/v ethanol) reinforcement (20 μl) into the well along with activating a light and a tone stimulus (80 dB). Responses on the “inactive lever” were recorded, but did not result in any stimulus consequences or reinforcement delivery. The position of the “active” lever (left vs. right of well) was counterbalanced across subjects. Stimulus events and responses were controlled and monitored using Med PC, Version IV software (Med Associates). At the end of each session, any residual fluid left in the well was collected with a pipette, measured, and subtracted from the total volume of alcohol delivered. The corrected volume was used to calculate g/kg alcohol intake during the 20-min daily sessions. Male and female mice were tested in separate chambers throughout the experiments (8 chambers/sex).

All set-shifting and self-administration experiments were conducted during the rats’ active (dark) cycle in standard Plexiglas self-administration chambers (30 × 20 × 20 cm) that were enclosed in sound attenuating cubicles with a ventilation fan (Med Associates, St. Albans, Vermont) and linked to a computerized data collection program (MED PC, Med Associates). Importantly, the self-administration chambers were located in a different room from the set-shifting chambers, and stimuli in the chambers were altered to prevent contextual association with the set-shifting chamber.

Self-administration, extinction, and reinstatement were performed in
standard operant chambers (30 × 20 × 20 cm) enclosed in sound
attenuating cubicles with a ventilation fan (Med Associates, St. Albans,
Vermont) and linked to a computerized data collection program (MED PC, Med
Associates). Each chamber was equipped with two retractable levers, a white
stimulus light above each lever, house light, and tone generator (78 dB, 4.5
kHz). A house light remained on throughout each experimental session. For meth
self-administration, infusion tubing was enclosed in steel spring leashes
(Plastics One Inc., Roanoke, VA) and connected to the infusion harness. A
weighted swivel apparatus (Instech, Plymouth Meeting, PA) was suspended above
the box to allow for free movement within the chamber. For sucrose
self-administration, a food magazine was inserted between levers, allowing the
delivery of a sucrose pellet (45mg, Bioserve, MD).