Study of propranolol and its related adrenoceptor antagonists on changes of gastric electrical parameters induced by...

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 beta-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 beta2-antagonist, produced the similar but less significant effects in the same experimental setting. Metroprolol, a beta1-adrenoceptor blocker, given by the similar doses did not produce significant effects. Nonselective beta-adrenoceptor blocker, nadolol but not the beta- and alpha-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 beta2-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.