Evidence for A1 adenosine receptor–mediated inhibition of peristalsis in the guinea-pig isolated ileum

Segments of ileum (5-30 cm from the caecum) were obtained from male guinea-pigs (Dunkin Hartley, 300-500g), cannulated at the oral and aboral ends and secured horizontally in 10 ml baths containing Krebs’ solution maintained at 37oC and oxygenated with 95%O2 and 5%CO2. Regular peristalsis was obtained by infusing saline solution into the lumen using the method described previously (Costall et al., 1993). All drugs were added to the serosal side, antagonists and the vehicle were equilibrated for at least 30 min before the addition of adenosine. Adenosine was added cumulatively at 6-8 min intervals once a regular peristalsis was obtained. Any increase in the threshold for peristalsis was measured from the maximum threshold in the 6 min period before the addition of adenosine and expressed as a percentage change to the possible maximum increase in threshold (taken as 4 cm, the position of the outlet tube) when peristalsis was abolished. All values are presented as mean±s.e.mean and statistical comparisons between the different treatments were made using one way ANOVA followed by Dunnett's t test.