Abstract

The expression, maintenance, and extinction of a cocaine-induced conditioned place preference was studied using a three-chamber 'unbiased' apparatus. During training, rats were given four 20 minute pairings of one chamber with cocaine (Experiment 1, 3 and 4: 10 mg/kg, IP; Experiment 2: 5, 10, and 20 mg/kg, IP) and four of the other with saline on alternate days. In 15 minute tests for preference rats were placed in the centre choice region drug-free with access to the entire apparatus. In Experiment 1, rats demonstrated a conditioned place preference for the cocaine-paired side, accompanied by a decrease in chamber transitions over the duration of the test. In Experiment 2, after training at all doses, strong preferences for the cocaine-paired chamber were evident. The preference was maintained in tests given at 2, 4, and 6 weeks. In Experiment 3, after training, rats were given repeated tests in a non-drugged state (extinction). In Experiment 4, extinction training consisted of pairing each chamber with saline on four occasions. Both methods led to the abolition of the conditioned place preference. Following extinction in both experiments rats were given a priming injection of cocaine (5 mg/kg, IP) which reinstated the conditioned place preference. These results indicate that the development, maintenance, and extinction of a conditioned place preference follow the principles of associative learning and suggest that this procedure can be used to study drug-induced reinstatement.