Effect of Acetylated Derivatives of some Sympathomimetic Amines on the Isolated Auricles and Tracheal Chain of the Guinea‐pig

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Abstract
The effects of acetylation of the sympathomimetic amines tyramine, amphetamine, ephedrine, phenylephrine, orciprenaline, salbutamol and their O- and N-acetyl derivatives, and the effects of reserpine or physostigmine pretreatment on the isolated auricles and tracheal chain of guinea-pigs were studied. All the parent drugs relaxed the tracheal chain and had a positive inotropic and chronotropic effect on the isolated auricles; only amphetamine contracted the tracheal chain. O-acetylation of these sympathomimetic amines generally decreased less chronotropic than inotropic action on the isolated auricles. O-acetylation of tyramine actually increased the positive chronotropic activity of drug. As a rule, O-acetylation also decreased the .beta.-adrenergic effect of these compounds on the tracheal chain, but not so markedly as on the isolated auricles. N-acetylation generally abolished the adrenergic effects of these sympathomimetic amines on the isolated auricles and decreased those effects on the tracheal preparation. N,O-triacetylation of salbutamol abolished the stimulating effect of the parent drug on the auricles but increased the relaxant activity on the trachea. Physostigmine antagonized the effects of O-acetyltyramine and O-triacetylorciprenaline but not those of tyramine and orciprenaline on the trachea preparation. Acetylation of the sympathomimetic amines may be utilized for the development of specific bronchodilators, and O-acetylation, for inducing drug latentiation.