Interaction between dopamine and adenosine A2A receptors as a basis for the treatment of Parkinson's disease.

The adenosine A2A receptor antagonist SCH 58261 increases the turning behaviour induced by L-dopa in unilaterally 6-hydroxydopamine (6-OHDA)-lesioned rats. In this study we have evaluated the effect of a chronic intermittent administration of L-dopa or SCH 58261 plus L-dopa on turning behaviour. Chronic intermittent administration of SCH 58261 plus L-dopa produced a stable turning behaviour during the course of the treatment, whereas L-dopa alone produced a progressive increase in turning behaviour. Moreover, repeated administration of SCH 58261 failed to produce tolerance to its ability to potentiate L-dopa-induced turning behaviour. The results indicate that SCH 58261 is effective after chronic administration and suggest that SCH 58261 plus L-dopa, differently from Ldopa alone, does not produce alterations in motor responses during the course of the treatment.