Xanthine derivatives as adenosine receptor antagonists.

The potency of a series of xanthine derivatives as adenosine antagonists was studied in fat cells (A1-receptors) and hippocampal slices (A2-receptors) and on L-[3H]phenylisopropyladenosine (PIA) binding in membranes from rat cortex. The order of potency in all three tests systems was: diethyl-8-phenyl-theophylline greater than 8-phenyltheophylline greater than 8-p-sulfophenyltheophylline greater than verrophylline greater than isobutylmethylxanthine greater than theophylline caffeine greater than theobromine. Enprofylline was about 20 times more potent in the hippocampus system than in the other two systems.