The purpose of the present study was to evaluate the effect of
isoprenaline on gastric
antral motility in conscious dogs with
gastric fistula, using intraluminal strain-gauge transducers. Infusion of
bethanechol increased the motility for both frequency and strength.
Isoprenaline, a beta 1- and beta 2-agonist, was used alone and in conjunction with selective blockade of beta 1 and beta 2 receptors. The stimulated
antral motility was dose-dependently inhibited by
isoprenaline. The effect was significantly blocked by the beta 1 + beta 2-adrenoceptor blocker
propranolol and by using in conjunction the beta 1-adrenoceptor blocker
practolol and the beta 2-adrenoceptor blocker
H 35/25.
H 35/25 and particularly
practolol reduced the effect of
isoprenaline to some extent, but the reduction was not of statistical significance. This indicates that
isoprenaline acts on
antral motility through both beta 2 and beta 1 receptors. Dose-response experiments with five logarithmically increasing doses of
bethanechol and one dose of
isoprenaline showed inhibition of a non-competitive type.