Cocaine conditioned behavior: a cocaine memory trace or an anti-habituation effect

Whether cocaine locomotor conditioning represents a cocaine positive effect; i.e., a Pavlovian cocaine conditioned response; or, a cocaine negative effect; i.e., interference with habituation to the test environment, is a subject of some controversy. Three separate experiments were conducted to compare the behavior (locomotion and grooming) of separate groups of rats given 1, 9 or 14 cocaine (10 mg/kg) treatments paired/unpaired with placement into an open-field arena. The behavior of the cocaine groups on subsequent saline tests were compared with the habituation rates of saline treated rats. After one cocaine pairing with the test environment, the subsequent behavior of the cocaine paired group on saline tests was similar to a non-habituated control group. In the two experiments with repeated cocaine pairings to the test environment, the subsequent behavior of the cocaine treated groups did not parallel that of the non-habituated saline control groups. These results were not explicable in terms of cocaine anti-habituation effects. It is suggested that cocaine contextual cues paired with cocaine treatment can activate cocaine memory traces which with subsequent cocaine treatments are reinforced and strengthened. In this way repeated cocaine use can forge conditioned stimulus connections to the cocaine behavioral response that are highly resistant to extinction.