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. Author manuscript; available in PMC: 2009 Apr 1.
Published in final edited form as: Pharmacol Biochem Behav. 2007 Dec 15;89(2):188–199. doi: 10.1016/j.pbb.2007.12.009

Fig. 5. Morphine exposure differentially impacts subsequent morphine-induced locomotor responses in rats treated as periadolescents or adults.

Fig. 5

Periadolescent male (A) and female (C) and adult male (B) and female (D) rats were treated with one of four injection regimens: five days of saline (S-S-S-S-S), one day of morphine (10 mg/kg/day) followed by four days of saline (M-S-S-S-S), three days of 10 mg/kg morphine (M-M-M-S-S), or five days of 10 mg/kg morphine (M-M-M-M-M). Five weeks later, horizontal activity was assessed (2 h) immediately following the administration of saline or increasing doses of morphine. Each data point represents the mean ± S.E.M. (n=6–8). *Indicates a significant difference from S-S-S-S-S treated cohorts; mixed three-factor ANOVA, Newman-Keuls post hoc, P<0.05.