Extinction procedures abolish conditioned stimulus control but spare sensitized responding to amphetamine.

The effect of extinction on previously established environment-specific sensitization of the locomotor activating effects of 1.0mg/kg d-amphetamine sulfate was studied in an attempt to investigate the relation between sensitization and conditioning of the drug effect. During the conditioning phase, groups of eight rats each were administered drug, i.p., prior to being placed in activity boxes and saline in their home cages (paired group), drug in the home cages and saline in the activity boxes (unpaired group), or saline in both environments. Evidence for conditioning and environment-specific sensitization was found following the conditioning phase in tests during which animals were administered saline or amphetamine, respectively. On a final test for environment-specific sensitization that followed the extinction phase (during which all animals received saline injections in both the activity boxes and the home cages), sensitized responding to amphetamine was found in both the paired and unpaired groups, suggesting that prior to extinction the expression of sensitization in the unpaired group had been under inhibitory control.