Acute opioid tolerance and dependence were induced in mice by morphine (100mg/kg, s.c.). When mice were treated with HJC0122 (1, 10 mg/kg, i.p.) 30 min before the induction dose of morphine, HJC0122 significantly prevented the development of acute opioid (A) tolerance and (B) dependence. When mice received HJC0122 (1, 10 mg/kg, i.p.) 30 minutes before the test dose of morphine (10 mg/kg, s.c.), HJC0122 significantly reversed the established opioid (C) tolerance and (D) dependence in a dose dependent manner. Data are expressed as the mean ± S.E.M. *P<0.05; **P<0.01; ***P<0.001 compared with saline group; ##P<0.01; ###P<0.001 compared with morphine alone group.