Age-related alteration of the adenosine/dopamine balance in the rat striatum

An antagonistic interaction between adenosine A(2A)-and dopamine D2- receptors has been described. Radioligand binding experiments showed a predominant reduction in the number of D2 vs. A(2A)-receptors in the striatum of aged compared to young rats. The A(2A)-receptor-mediated antagonistic modulation of D2-receptor binding remained unchanged in aged animals. In striatal homogenates a significant increase in adenosine and no change in dopamine content was found in aged vs. young rats. These results reveal the existence of an age-dependent imbalance of adenosinee vs. dopamine in favor of adenosine, which involves both presynaptic and postsynaptic mechanisms.