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THE SELECTIVITY OF β‐ADRENOCEPTOR ANTAGONISTS ON CARDIOVASCULAR AND BRONCHODILATOR RESPONSES TO ISOPRENALINE IN THE ANAESTHETIZED DOG
Author(s) -
DALY M.J.,
FLOOK JUDITH J.,
LEVY G.P.
Publication year - 1975
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.1975.tb07347.x
Subject(s) - practolol , chronotropic , acebutolol , isoprenaline , propranolol , heart rate , bronchodilator , antagonist , medicine , blood pressure , pharmacology , endocrinology , anesthesia , receptor , asthma , stimulation
1 The actions of five β‐adrenoceptor antagonists, chosen because of reported differences in their selectivities, were compared using the positive chronotropic, vasodepressor and bronchodilator responses to isoprenaline in anaesthetized dogs. 2 Propranolol was a potent antagonist of the isoprenaline responses in all three systems. 3 Practolol and acebutolol (M & B 17,803) blocked the positive chronotropic responses to isoprenaline to a greater extent than the vasodepressor or bronchodilator responses. 4 Butoxamine and α‐methyl dichloroisoprenaline showed the opposite selectivity, blocking the vasodepressor and bronchodilator responses to isoprenaline to a greater extent than positive chronotropic responses. However, both drugs were considerably less potent than the other antagonists studied and their selectivities were less clear‐cut than those of practolol or acebutolol. 5 All the antagonists lowered the resting heart rate and to a lesser extent the diastolic blood pressure. The effects of propranolol, practolol and acebutolol on heart rate probably result from cardiac β‐adrenoceptor blockade. With butoxamine and α‐methyl dichloroisoprenaline, however, the effects on heart rate probably result from a direct cardiodepressant action. 6 The relevance of the results to the problem of the sub‐classification of β‐adrenoceptors is discussed.