Dyskinesias represent a debilitating complication of levodopa therapy for Parkinson's disease (PD). While we recently demonstrated that levodopa-induced dyskinesia results from increased dopamine D₁ receptor-mediated transmission, we also questioned the possible role of subcellular localization of D₁ and D₂ receptors in mediating these effects as we previously showed that D₁ receptors undergo differential trafficking in striatal neurons of non-dyskinetic PD patients. Taking advantage of a monkey brain bank, we here report changes affecting the cellular and subcellular distribution of D₁ and D₂ dopamine receptors within the striatum of three experimental groups: normal, parkinsonian and dyskinetic l-dopa-treated parkinsonian animals. Our studies at both light and electron microscopy levels show a recruitment of D₁ receptor at the plasma membrane of striatal neurons in the parkinsonian animals and a strong increase of D₁ expression both at the membrane and in cytoplasm of dyskinetic animals, whereas D₂ receptor distribution is only modestly affected in all conditions. Our results rule out the hypothesis of a pathological overinternalization of dopamine receptors in levodopa-induced dyskinesia but raise the possibility for involvement of D₁ receptors in the priming phenomenon through massive and sudden internalization in response to the first ever administration of l-dopa and for an altered homologous desensitization mechanism in dyskinesia leading to an increased availability of D₁ receptors at membrane. Further experiments including parkinsonian monkeys chronically treated with l-dopa that show no dyskinesia and parkinsonian monkeys treated only once with l-dopa are now necessary to confirm our hypothesis.