Adenosine A2A agonist CGS 21680 decreases the affinity of dopamine D2 receptors for dopamine in human striatum

Adenosine A2A receptors (A2AR) and dopamine D2 receptors (D2R) are highly concentrated in the striatum, where they are co-localized and exert reciprocal antagonistic interactions. It has been suggested that the A2R/D2R interactions might provide a therapeutic approach for basal ganglia disorders, such as Parkinson´s disease, and schizophrenia. In the present work evidence is presented for the existence of an A2AR/D2R interaction in human brain by using quantitative autoradiography. The areas analyzed were the dorsal caudate nucleus and putamen. Parallel studies were performed in rat striatal sections. The A2AR agonist CGS 21680 was found to significantly increase IC50 values of competitive inhibition curves of the D2R/D3R antagonist [I-125]iodosulpiride vs dopamine both in rat striatal and human striatal brain sections.