The effects of some β‐adrenoreceptor blocking drugs on the uptake and release of noradrenaline by the heart

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Abstract
1 The potencies of some β-adrenoreceptor blocking drugs in reducing noradrenaline uptake by the isolated heart were compared with their potencies in reducing the release of noradrenaline from the heart by tyramine. 2 Of the drugs tested, propranolol, pronethalol and dichloroisoprenaline were the most potent in blocking uptake and release of noradrenaline, although none was at potent as cocaine; MJ 1999 and I.C.I. 50172 were only weakly effective. 3 Pronethalol and dichloroisoprenaline each reduced release of noradrenaline by tyramine in the concentration range (10−7–10−6M) where blockade of responses to tyramine was apparent; with these drugs both reduction of noradrenaline release and β-receptor blockade contribute to the reduction in responses to tyramine. 4 Potency of β-receptor blocking drugs in reducing noradrenaline uptake is unrelated to potency in blocking β-receptors; Kö 592 blocks β-receptors without affecting noradrenaline uptake.
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