The actions of different adrenoceptor antagonists on gastric potential difference (PD), electrical current (I) and resistance (R) were studied, using the voltage clamp technique. In an isolated gastric mucosal tissue, 5% ethanol was able to reduce the PD and I across the gastric mucosa. Direct incubation with propranolol 10–4 mol/l either from the mucosal or submucosal sides attenuated such effects. Intraperitoneal administration of propranolol (2.5–10 mg/kg), a nonselective β-adrenoceptor blocker with significant membrane-stabilizing activity, given 30 min before the preparation of the gastric tissue, not only alleviated the fall in PD and I across the gastric mucosa, but also increased the R of the stomach tissue. Butoxamine, a selective β2-antagonist, produced the similar but less significant effects in the same experimental setting. Metroprolol, a β1-adrenoceptor blocker, given by the similar doses did not produce significant effects. Nonselective β-adrenoceptor blocker, nadolol but not the β- and α-adrenoceptor blocker, labetalol, also significantly preserved the decrease of PD induced by ethanol, but to a lesser extent. These findings suggest that blockade of the β2-receptors in the gastric mucosa together with membrane-stabilizing activity could improve the integrity of the gastric mucosa, and these effects are probably acting through its direct action on the tissue.

Keywords:
β-Adrenoceptor antagonist, Potential difference, Current, Resistance
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1998
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