Dopamine D₂ long (D₂L) and D₂ short (D₂S) isoforms of the D₂ receptor play an important role in psychostimulant‐induced neuronal adaptations. In this study, we used quantitative real‐time PCR to specifically amplify these two splice variants to examine their mRNA expression in the dorsal striatum (dStr), nucleus accumbens (NAc) and the ventral tegmental area (VTA) of amphetamine‐sensitized C57BL/6 mice. We found a significant increase in D₂L mRNA in the VTA and dStr of amphetamine‐treated mice that positively correlated with the sensitized locomotor response. We also found a significant increase in D₂S mRNA in the VTA. We further examined the role of the Ca_v1.3 subtype of L‐type Ca²⁺ channels in up‐regulation of D₂L and D₂S mRNA in the VTA. Amphetamine‐pretreated Ca_v1.3 wild‐type (Ca_v1.3^+/+) mice exhibited sensitized behavior and a significant increase in D₂L and D₂S mRNA compared with saline‐pretreated mice Amphetamine‐pretreated homozygous Ca_v1.3 knockout (Ca_v1.3^–/–) mice did not exhibit sensitized behavior. There was a significant increase in D₂S mRNA, but not D₂L mRNA. In conclusion, our results find that amphetamine increases D₂L mRNA expression in the dStr and the VTA, an adaptation that correlates with expression of sensitized behavior and dependence on Ca_v1.3 Ca²⁺ channels.