Selective activity of bamifylline on adenosine A1-receptors in rat brain

The activity of the xanthine derivative bamifylline on central adenosine A1 and A2 receptors has been evaluated with radio-receptor binding in rat brain in comparison with other structure-related compounds. Bamifylline displaced 3H-Cyclo-hexyl-adenosine and 3H-Diethyl-8-phenyl-xanthine with a potency similar to that of 8-phenyl-theophylline, suggesting a high activity on A1-receptor subtype. In contrast, when 3H-N-Ethyl-carboxamido adenosine was used to label A2 adenosine receptors in rat striatum, bamifylline displayed a lower activity comparable to that of enprofylline, an alkyl- xanthine considered a very weak antagonist of adenosine receptors. By calculating for each xanthine derivative its relative potency at A1 and A2 receptors (A2/A1 ratio), bamifylline turned out being the most selective A1 adenosine receptor antagonist so far tested.