CPP paradigm in this study. (A) Timeline of CPP procedure. (B) Acquisition and extinction of cocaine-induced CPP. CPP score is the time spent in the drug-paired chamber versus in non-drug-paired chamber. Baseline is examined on day 0. CPP test 1 is performed on day 14 following 13-day CPP training and drug administration. CPP test 2 is carried out on day 26 after 12-day CPP extinction training. n = 12 ~ 16 rats per group. **p < 0.01 vs. baseline on day 0.