Place avoidance conditioning with D-amphetamine: the effect of screening and the use of preferred and non-preferred sides.

The effect of screening animals to identify unconditioned preferences for stimuli used in subsequent place conditioning, and the effect of pairing drug injections with originally most or least preferred stimuli were investigated in place conditioning with 0.5 and 2.0 mg/kg D-amphetamine. A choice test to identify conditioned approach and avoidance responses was given after every two end compartment drug trials until a total of 10 choice tests had been given. During drug trials, the drug was injected 15 min after the animal was placed in the end compartment and the animal remained in the end compartment for 30 min following drug injection. In confirmation of previous research from our laboratory, during choice tests, animals avoided the end compartment that had been paired with D-amphetamine and this avoidance occurred regardless of whether the animals had been initially screened or not, and regardless of whether the originally most or least preferred stimuli were used as the drug-associated end compartment.