The Journal of Neuroscience, March 19, 2008, 28(12):2970-2975; doi:10.1523/JNEUROSCI.5255-07.2008
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A Critical Role of the Adenosine A2A Receptor in Extrastriatal Neurons in Modulating Psychomotor Activity as Revealed by Opposite Phenotypes of Striatum and Forebrain A2A Receptor Knock-Outs
Hai-Ying Shen,1
Joana E. Coelho,1
Nobuhisa Ohtsuka,2
Paula M. Canas,4
Yuan-Ji Day,3
Qing-Yuan Huang,1
Nelson Rebola,4
Liqun Yu,1
Detlev Boison,5
Rodrigo A. Cunha,4
Joel Linden,3
Joe Z. Tsien,2 and
Jiang-Fan Chen1
1Molecular Neuropharmacology Laboratory, Department of Neurology and 2Department of Pharmacology, Boston University School of Medicine, Boston, Massachusetts 02118, 3Department of Medicine, University of Virginia, Charlottesville, Virginia 22908, 4Center for Neuroscience of Coimbra, Institute of Biochemistry, Faculty of Medicine, University of Coimbra, 3004-504 Coimbra, Portugal, and 5Robert S. Dow Neurobiology Laboratories, Legacy Research, Portland, Oregon 97232
Correspondence should be addressed to Dr. Jiang-Fan Chen at Department of Neurology, Boston University School of Medicine, 715 Albany Street, E301, Boston, MA 02118. Email: chenjf{at}bu.edu
The function of striatal adenosine A2A receptors (A2ARs) is well recognized because of their high expression levels and the documented antagonistic interaction between A2ARs and dopamine D2 receptors in the striatum. However, the role of extrastriatal A2ARs in modulating psychomotor activity is largely unexplored because of the low level of expression and lack of tools to distinguish A2ARs in intrinsic striatal versus nonstriatal neurons. Here, we provided direct evidence for the critical role of A2ARs in extrastriatal neurons in modulating psychomotor behavior using newly developed striatum-specific A2AR knock-out (st-A2AR KO) mice in comparison with forebrain-specific A2AR KO (fb-A2AR KO) mice. In contrast to fb-A2AR KO (deleting A2ARs in the neurons of striatum as well as cerebral cortex and hippocampus), st-A2AR KO mice exhibited Cre-mediated selective deletion of the A2AR gene, mRNA, and proteins in the neurons (but not astrocytes and microglial cells) of the striatum only. Strikingly, cocaine- and phencyclidine-induced psychomotor activities were enhanced in st-A2AR KO but attenuated in fb-A2AR KO mice. Furthermore, selective inactivation of the A2ARs in extrastriatal cells by administering the A2AR antagonist KW6002 into st-A2AR KO mice attenuated cocaine effects, whereas KW6002 administration into wild-type mice enhanced cocaine effects. These results identify a critical role of A2ARs in extrastriatal neurons in providing a prominent excitatory effect on psychomotor activity. These results indicate that A2ARs in striatal and extrastriatal neurons exert an opposing modulation of psychostimulant effects and provide the first direct demonstration of a predominant facilitatory role of extrastriatal A2ARs.
Key words: adenosine A2A receptor; cocaine; PCP; psychomotor activity; striatum A2AR knock-out; forebrain A2AR knock-out
Received Nov. 27, 2007;
revised Dec. 26, 2007;
accepted Jan. 16, 2008.
Correspondence should be addressed to Dr. Jiang-Fan Chen at Department of Neurology, Boston University School of Medicine, 715 Albany Street, E301, Boston, MA 02118. Email: chenjf{at}bu.edu
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