Adenosine induces contractions in suncus ileum.

Purinoceptor-mediated responses were characterized in the ileum of Suncus murinus. Adenosine as well as adenosine 5'-triphosphate (ATP) contracted the ileum in a concentration-dependent manner. Contractile responses to transmural electrical stimulation were attenuated by adenosine only at high concentrations. Theophylline competitively blocked the adenosine-induced contraction. Atropine also inhibited the adenosine-induced contraction but in a non-competitive manner. The ATP-induced contraction was not affected by theophylline, atropine or alpha, beta-methylene ATP. Indomethacin shifted the concentration-response curves for adenosine and ATP to the right. These results suggest that adenosine elicited contractions via direct stimulation of postsynaptic P1-purinoceptors and postsynaptic potentiation of the acetylcholine response. Suncus ileum will be a unique model for the analyses of purinoceptor-mediated responses.