MPD (Mallinckrodt, St Louis, MO, USA) and DA D1 and D2 receptor antagonists, R(+) SCH-23390 hydrochloride and S(−)-raclopride (+)-tartrate (Sigma-Aldrich Corp, St Louis, MO, USA), respectively, were used. All injections were made fresh, dissolving the drug in 0.9% isotonic saline, equalized to 0.8 mL, and injected, via intraperitoneal (IP) route, in the morning. In previous MPD dose–response behavioral experiments ranging from 0.1 to 40.0 mg/kg, it was observed that 2.5 mg/kg of MPD elicited behavioral sensitization when given in the morning;36 (link),41 (link)–45 (link) therefore, this dosage (2.5 mg/kg) was selected. Previous studies used a range of 0.2–0.5 mg/kg SCH-23390 selective D1 DA antagonist and 0.3–0.4 mg/kg raclopride selective D2 DA antagonist, which were effective in modulating the psychostimulant effect on animal behavior and on the prefrontal cortex.19 (link),46 (link) Therefore, we chose SCH-23390, 0.4 mg/kg, and D2 DA antagonist raclopride, 0.3 mg/kg, to study the role of the D1 and D2 DA receptors in the effects of acute and chronic MPD exposure on animal behaviors.