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Pronethalol and various sympathomimetic amines exhibit unspecific, noncompetitive antagonism of butyrylcholine and tyramine in guinea-pig isolated atria, distinct from competitive beta-blockade of noradrenaline.
The adrenaline beta-receptor blocking drug, pronethalol, and the sympathomimetic amines, (-)-ephedrine, (-)-amphetamine, dexamphetamine, (-)-Psi-ephedrine and tyramine, inhibited the sympathomimetic effects of butyrylcholine and tyramine on the guinea-pig isolated atrium. Being reversible and noncompetitive, this antagonism was unspecific and not due to blockade of adrenaline receptors, although pronethalol inhibited the effect of noradrenaline competitively.
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Benfey et al. (1964) studied this question.
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