An aryl p-(trifluoromethyl) substituent increases the affinity of 1, 3-disubstituted 8- phenylxanthines at Aa,-adenosine receptors, while having little effect on affinity at AI- adenosine receptors. In contrast, an aryl p-(trifluoromethyl) substituent has little effect on affinity of 3, 7-disubstituted and 1, 3, 7-trisubstituted 8-phenylxanthines. An aryl p-sulfo substituent reduces affinity of all 8-phenylxanthines at AI-and Ah-adenosine receptors. An ...
