It is reported that Rotundine (l-THP) possesses a blocking effect on dopamine D1 and D2 receptors and can inhibit physical dependence in morphine dependent mice and significantly reduce the development of the conditional place preference induced by morphine in mice. On day 1 and 7, there is no difference in locomotor counts between the Rotundine groups (6.25, 12.5, and 18.75 mg/kg) and saline group [F(3, 37)=1.360, P>0.05, F(3, 37)=0.348, P>0.05, respectively]. Locomotor counts are greatly increased in the oxycodone group compare with the saline group. Rotundine at doses of 6.25, 12.5, and 18.75 mg/kg antagonizes hyperactivity induced by oxycodone [F(4, 60)=15.76, P<0.01]. Rotundine (6.25, 12.5 mg/kg) does not affect the magnitude of sensitization, but there is a marked difference between oxycodone+oxycodone group and Rotundine (18.75 mg/kg)+oxycodone+oxycodone group, indicating that Rotundine (18.75 mg/kg) greatly inhibits the development of oxycodone sensitization [F(4, 62)=8.766, P<0.01].