D2 and D3 receptors are subtypes of D2-like dopamine receptors, and both have been shown to be involved in drug addiction with different roles. Their mRNA are expressed moderately highly in striatum, where dopamine plays a crucial role in drug reward pathways, and are expressed at low level in hippocampus, where dopamine has recently been implicated in the long-term, memory components of addiction. In our studies, we did functional and gene expression assays on dorsal and ventral fractions of striatum and hippocampus from eight cocaine-treated and control rats. We found that the potency of D2/D3 receptor agonist was highest in dorsal striatum. The potency of receptor activity was more correlated with D2 receptor gene expression than D3 receptor expression. Cocaine did not show any convincing effect on D2 and D3 receptor function and gene expression.