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The influence of the intrinsic sympathomimetic activity of β‐adrenoceptor antagonists on haemodynamic effects in anaesthetized dogs
Author(s) -
Wale Janet L.,
Austin M.,
Conway J.,
Reeves M.
Publication year - 1979
Publication title -
clinical and experimental pharmacology and physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 103
eISSN - 1440-1681
pISSN - 0305-1870
DOI - 10.1111/j.1440-1681.1979.tb00002.x
Subject(s) - practolol , atenolol , pindolol , propranolol , heart rate , hemodynamics , anesthesia , cardiac output , medicine , blood pressure , cardiology
Summary 1. The effects of propranolol, atenolol (ICI 66,082), practolol and pindolol on heart rate and maximal left ventricular dp/dt , atrioventricular conduction time, mean aortic flow and diastolic blood pressure during cardiac pacing were investigated over a wide dose range (0.025‐4.0 mg/kg, i.v.) in dogs anaesthetized with pentobarbitone. 2. Propranolol and atenolol produced similar reductions in haemodynamic parameters. Propranolol had no further effect in dogs pretreated with atenolol. 3. Practolol tended to cause smaller reductions in the haemodynamic parameters than either propranolol or atenolol. Subsequent administration of propranolol still had some depressant activity. 4. Pindolol produced a biphasic response, with depression of cardiac function at the low doses (0.025 and 0.1 mg/kg), but a reversal of effect as the dose was increased. 5. It is therefore concluded that, in anaesthetized dogs, the intrinsic activity of practolol and pindolol limits the fall in heart rate, cardiac conduction, aortic flow and maximal dp/dt observed with β ‐adrenoceptor blockade. With pindolol, however, the influence of intrinsic activity is observed only in high doses related to β ‐adrenoceptor blockade.