Dopamine D₁ and D₂ receptor contributions to L-DOPA-induced dyskinesia in the dopamine-depleted rat

Using a rat model of L-DOPA-induced dyskinesia (LID), the contributions of dopamine D₁ and D₂ receptors to axial, limb, and orolingual (ALO) abnormal involuntary movements (AIMs) elicited by L-DOPA were examined. Chronic L-DOPA-treated rats received the D₁ receptor antagonist SCH23390 (0.01, 0.1, and 1.0 mg/kg; ip), the D₂ receptor antagonist Eticlopride (0.01, 0.1, and 1.0 mg/kg; ip), a mixture of both antagonists (0.01, 0.1, 1.0 mg/kg each; ip), or vehicle 30 min prior to L-DOPA (6 mg/kg; ip) + Benserazide (15 mg/kg; ip). SCH23390 (0.1 and 1.0 mg/kg) significantly reduced axial and limb AIMs, while the same doses of Eticlopride significantly decreased axial, limb, and orolingual AIMs. Co-administration of SCH23390 + Eticlopride significantly reduced axial (0.01, 0.1 and 1.0 mg/kg), limb (0.1 and 1.0 mg/kg ), and orolingual (0.1 and 1.0 mg/kg) AIMs. These results indicate the importance of D₁ and D₂ receptors to LID and further validate the rat AIMs model.