Brain Advance Access originally published online on March 19, 2004
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Brain, Vol. 127, No. 5, 1075-1084, 2004
© 2004 Guarantors of Brain
doi: 10.1093/brain/awh128
Increased adenosine A2A receptors in the brain of Parkinsons disease patients with dyskinesias
1 Molecular Endocrinology and Oncology Research Center, Laval University Medical Center (CHUL) and Faculty of Pharmacy, Laval University, Québec, 2 Division of Neurology, University of Saskatchewan, Royal University Hospital, Saskatoon, Canada, 3 Institute for Brain Research, Faculty of Medicine, University of Vienna, Vienna, Austria and 4 Neuroscience Research Unit, Laval University Medical Center (CHUL) and Department of Medicine, Laval University, Québec, Canada
Correspondence to: Dr Thérèse Di Paolo, Molecular Endocrinology and Oncology Research Center, Laval University Medical Center (CHUL), 2705 Boul Laurier, Ste-Foy, Québec, Canada G1V 4G2E-mail: therese.dipaolo{at}crchul.ulaval.ca
Brain adenosine A2A receptors have recently attracted considerable attention because of their interaction with the dopaminergic system and as potential targets for Parkinsons disease pharmacotherapy. Post mortem adenosine A2A receptor mRNA and [3H]SCH 58261- specific binding to adenosine A2A receptor were studied in the brain of Parkinsons disease patients using in situ hybridization and receptor binding autoradiography, respectively. Fourteen levodopa-treated Parkinsons disease patients, of which seven developed dyskinesias and seven did not, were compared with nine controls. Nigrostriatal denervation was similar between dyskinetic and non-dyskinetic Parkinsons disease patients, as assessed with catecholamine concentrations and [125I]RTI-121-specific binding to dopamine transporters. A2A receptor mRNA levels (+129%; P < 0.01) and [3H]SCH 58261-specific binding (+32%, P < 0.01) were increased in the putamen (lateral and medial) of dyskinetic patients compared with controls. The increase of adenosine A2A receptor mRNA in dyskinetic Parkinsons disease patients was also significant compared with non-dyskinetic Parkinsons disease patients (+60%; P < 0.05) in the lateral putamen. Moreover, [3H]SCH 58261-specific binding to adenosine A2A receptors was increased in the external globus pallidus (+24%; P < 0.001) of Parkinsons disease patients compared with controls, regardless of the dyskinesigenic response to levodopa. No change of adenosine A2A receptors was observed in the caudate nucleus, whereas adenosine A2A receptor protein and mRNA levels in the internal globus pallidus were not different from background. These findings suggest that increased synthesis of adenosine A2A receptors in striatopallidal pathway neurons is associated with the development of dyskinesias following long-term levodopa therapy in Parkinsons disease.
Key Words: adenosine A2A receptors; motor complications; Parkinsons disease; putamen; SCH 58261
Abbreviations: AP = activator protein; A2AR = adenosine A2A receptor; GPe = external segment of the globus pallidus; LID = levodopa-induced dyskinesias; MPTP = 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine; OHDA = hydroxydopamine; PPE = preproenkephalin
Received August 8, 2003. Revised December 19, 2003. Accepted December 22, 2003.
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