Dose-dependent effects of methamphetamine on behavioral sensitization. Male, Swiss Webster mice (n = 12 per group) were injected with saline or methamphetamine (Meth; 0.1, 0.5, and 1 mg/kg, i.p.) on days 1–7. Following an 8-day drug-free period, the animals were challenged with either saline or methamphetamine (0.1, 0.5, and 1 mg/kg, i.p.) on day 15. Repeated administration of methamphetamine (0.5 and 1 mg/kg) on days 1–7 resulted in behavioral sensitization on day 15. Data are reported as mean ± SEM. *p < 0.05, **p < 0.01 vs. Meth (day 1), post hoc Dunnett’s tests