Role of adenosine A2A receptors in parkinsonian motor impairment and L-DOPA-induced motor complications

Adenosine A(2A) receptors have a unique cellular and regional distribution in the basal ganglia, being particularly concentrated in areas richly innervated by dopamine such as the caudate-putamen and the globus pallidus. Adenosine A(2A) receptors are selectively located on striatopallidal neurons and are capable of forming functional heteromeric complexes with dopamine D-2 and metabotropic glutamate mGlu5 receptors. Based on the unique cellular and regional distribution of this receptor and in line with data showing that A(2A) receptor antagonists improve motor symptoms in animal models of Parkinson's disease (PD) and in initial clinical trials, A(2A) receptor antagonists have emerged as an attractive non-dopaminergic target to improve the motor deficits that characterize PD. Experimental data have also shown that A(2A) receptor antagonists do not induce neuroplasticity phenomena that complicate long-term dopaminergic treatments. The present review provides an updated summary of results reported in the literature concerning the biochemical characteristics and basal ganglia distribution of A(2A) receptors. We subsequently aim to examine the effects of adenosine A(2A) antagonists in rodent and primate models of PD and Of L-DOPA-induced dyskinesia. Finally, concluding remarks are made on post-mortem human brains and on the translation of adenosine A(2A) receptor antagonists in the treatment of PD. (C) 2007 Elsevier Ltd. All rights reserved.