ATP, β-γ-methylene-ATP,and adenosine inhibit non-cholinergic non-adrenergic transmission in rat urinary bladder

ATP and adenosine caused a dose-dependent and reversible inhibition of the atropine-resistant contraction response to transmural nerve stimulation in the rat urinary bladder. Both purines also inhibited contraction responses to acetylcholine and direct muscle stimulation, indicating a postjunctional effect on the transmission. It seems as ATP per se inhibits the excitatory transmission, because the stable ATP-analogue β-γ-methylene-ATP was inhibitory as well, and because exogenous adenosine deaminase annulled the inhibition by adenosine but not that by ATP or β-γ-methylene-ATP. Blockade of purine in-activation enhanced the inhibitory action of ATP and adenosine, and by itself inhibited the transmission. These results are consistent with the possibility that endogenous purines may modulate non-cholinergic non-adrenergic excitatory transmission in the rat urinary bladder.