Abstract
The concentration-effect curves were established for the action of isoproterenol on the tracheal muscle of guinea pigs pretreated with such beta-adrenergic blocking agents as H 56/28 (1-(ο-allylphenoxy)-3-iso-propylamino-2-propanol), propranolol, pronethalol, and methoxamine. Then analysis was made of the antagonistic effect of beta-adrenergic blocking agents against isoproterenol and of the mode of action of isoproterenol and beta-adrenergic blocking agents at the adrenergic receptor.
1) The ratio of the intensity of the antagonistic effect of propranolol, H 56/28, pronethalol, and methoxamine was found to be 1: 1.5: 1/18: 1/1000; H 56/28 exerted the most intense antagonistic action.
2) When analysis was made of the concentration-effect curves established for the antagonistic action of beta-adrenergic blocking agents against isoproterenol in two different way of plotting, it could be said that the agonist competes with the antagonist for the receptor of the tracheal muscle.
3) Isoptoterenol showed a strong beta-adrenergic receptor activity on the trachea of guinea pigs. And yet it can not be said that the drug has no alpha-adrenergic receptor activity.
