Silicon-based microphysiometry, measuring extracellular acidification
rate of cells in culture, demonstrated that a series of diimidazo[1,2-
c:4',5'-e]pyrimidines were agonists at the human adenosine A(1) recept
or. (R)-(phenyl)-3H-diimidazo[1,2-c:4',5'-e]pyrimidine (2a) had an EC5
0 of 100 mu M and reached 90% of the E-max produced by R-PIA. (C) 1998
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