Adenosine A1 receptor blockade selectively potentiates the motor effects induced by dopamine D1 receptor stimulation in rodents.

An antagonistic interaction between adenosine A1 and dopamine D1 receptors has previously been found in the basal ganglia. However, direct evidence for a selective adenosine A1 antagonist-induced potentiation of dopamine D1-mediated motor activation is lacking. The systemic administration of the adenosine A1 antagonist 8-cyclopentyl-1,3-dimethylxanthine significantly potentiated the motor activating properties of the systemically administered dopamine D1 agonist SKF 38393 in both reserpinized mice and unilaterally 6-hydroxy-dopamine-lesioned rats. However, 8-cyclopentyl-1, 3-dimethylxanthine did not modify the motor effects of the dopamine D2 agonist quinpirole. The present work shows that an antagonistic interaction between adenosine A1 and dopamine D1 receptors may be involved in the motor activating effects of adenosine antagonists, like caffeine.