Effect of Isoprenaline on Bethanechol-Stimulated Gastric Antral Motility in Dogs with Gastric Fistula

Abstract

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 β₁- and β₂-agonist, was used alone and in conjuction with selective blockade of β₁ and β₂ receptors. The stimulated antral motility was dose-dependently inhibited by isoprenaline. The effect was significantly blocked by the β₁ + β₂-adrenoceptor blocker propranolol and by using in conjunction the β₁-adrenoceptor blocker practolol and the β₂-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 β₂ and β₁ receptors. Dose-response experiments with five logarithmically increasing doses of bethanechol and one dose of isoprenaline showed inhibition of a non-competitive type.

Key-words:

• Bethanechol
• β-blocking drugs
• dogs
• gastric antral motility
• isoprenaline
• strain-gauge transducer