Figure 5.

Effects of SCH23390 on morphine‐induced locomotor activation and sensitization in mice. (A) SCH23390 inhibited morphine‐induced locomotor activation. Mice were treated with saline, SCH23390 (0.03 mg·kg⁻¹, i.p.), morphine (10 mg·kg⁻¹, s.c., twice daily) or morphine plus SCH23390 for 7 consecutive days. Locomotor activity (distance travelled over a period of 180 min in m) was measured on days 1, 3, 5 and 7. (B) SCH23390 prevented the induction of behavioural sensitization from chronic morphine treatment. Seven days after the last administration of morphine, an additional challenge injection of morphine (10 mg·kg⁻¹, s.c.) was given to each group. (C) SCH23390 suppressed the expression of behavioural sensitization. The mice were chronically treated with morphine for 7 consecutive days. After another 7 days of abstinence, the animals were challenged with morphine with or without pretreatment with SCH23390. Values are expressed as the mean ± SEM (n = 10). *P < 0.05, significantly different from saline‐treated control group; ^# P < 0.05, significantly different from morphine alone‐treated group. One‐way ANOVA followed by Dunnett's post hoc tests.