MOLECULAR NEUROSCIENCEAre A3 adenosine receptors expressed in the brain?Rivkees, Scott A.1,2; Thevananther, Sundararajah1; Hao, Haiping1Author Information 1Section of Pediatric Endocrinology, Department of Pediatrics, Yale University Medical School, P.O. Box 208081, 464 Congress Ave., New Haven, CT 06520, USA 2Corresponding Author: Scott A. Rivkees Acknowledgements: Supported by National Institutes of Health Grant ROI-NS33539 and the Donaghue Medical Research Foundation. Received 11 January 2000; accepted 25 January 2000 NeuroReport: April 7, 2000 - Volume 11 - Issue 5 - p 1025-1030 Buy Abstract An increasing number of reports suggest a role for A3 adenosine receptors (A3ARs) in mediating adenosine action in the central nervous system. However, studies of A3AR localization in the brain have yet to be performed. To provide insights into the central sites of A3AR action, we compared patterns of A1 and A3AR mRNA and binding site expression in the brains of rats, mice and humans. We also assessed whether A3 agonists are selective for A3ARs. Whereas it was possible to detect high-level A1AR expression in many brain regions, it was not possible to detect either A3AR gene or binding site expression in the central nervous system. When we examined the affinities of the A3AR agonists Cl-IAB-MECA and IABMECA for A1ARs, we found that these compounds bound to A1ARs with high affinity. These observations suggest that studies using A3-agonists need to consider potential effects of A1ARs activation, as A1ARs are abundantly expressed in the nervous system whereas A3AR expression in the brain cannot be directly demonstrated. © 2000 Lippincott Williams & Wilkins, Inc.