DISSOCIATION OF NOVELTY-CONDITIONED AND COCAINE-CONDITIONED LOCOMOTOR-ACTIVITY FROM COCAINE PLACE CONDITIONING

High locomotor response to novelty is associated with ease of drug sel f-administration but does not predict greater place-conditioning effec ts of drugs. Yet, the latter reflects context conditioning and high re sponders (HR), compared to low responders (LR), show greater condition ed locomotor effects. Conditioned locomotor effects may occur in place conditioning, perhaps confounding its measure. To examine whether con ditioned locomotor effects occur in place conditioning, the present st udy classified rats as HR vs. LR by using approximately the two extrem e 15% percentiles of the distributions. The place conditioning and loc omotor sensitizing effects of cocaine were tested. In Experiment 1, HR rats exhibited more crossings between compartments but did not differ from LR rats In cocaine place conditioning. Further, both groups show ed increased crossings at test compared to baseline, indicative of a c onditioned locomotor effect. In Experiment 2, HR rats showed greater a cute locomotor activation to cocaine, whereas LR rats tend to show gre ater locomotor sensitization. Finally, in Experiment 3, HR rats showed habituation in locomotor responses, whereas LR rats did not. Results of these studies suggest that inherent and conditioned locomotor activ ity levels are dissociated from place-conditioning effects. (C) 1998 E lsevier Science Inc.