similar to those of Seale and Carney (1991): Day 1—Each mouse was introduced into the middle of the place conditioning apparatus. The guillotine doors were raised and the time spent on each side was automatically recorded during this 20 min baseline session. Days 2–4—There were a total of three conditioning days that totaled 40 min in duration. The guillotine doors remained closed during conditioning sessions. All mice were injected with saline and placed in the black compartment. After 20 min, each mouse was removed from the apparatus and briefly returned to its home cage. The animals were then injected with cocaine (3.2 mg/kg) and placed into the white compartment for an additional duration of 20 min. Day 5—Place preference was evaluated in a 20 min test. Each mouse was introduced into the middle of the apparatus and the guillotine doors were raised. The time spent on each side of the apparatus was recorded. The dependent measures included the time (seconds) spent on the drug- and saline-paired sides at baseline (Day 1) and test (Day 5). In addition, change in preference was calculated as time spent on the drug-paired side at test minus the time spent on the drug-paired side at
