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The effect of certain β‐adrenoceptor antagonists on overdrive suppression
Author(s) -
KELLIHER G.,
LUOTO JOANNE,
ROBERTS J.
Publication year - 1972
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.1476-5381.1972.tb08133.x
Subject(s) - practolol , propranolol , heart rate , reserpine , chemistry , medicine , pharmacology , antiarrhythmic agent , blood pressure , heart disease
Summary1 Propranolol, as the racemate and the (+)‐ and (–)‐isomers (400 μg/l.) and practolol (50 mg/l.) were tested for their effects on atrial and ventricular rates and on the duration of overdrive suppression (ODI) in isolated perfused cat hearts with surgically‐induced heart block. 2 Racemic propranolol and the (+)‐ and (–)‐isomers prolonged ODI and slowed the rate of the ventricular pacemaker; the (+)‐ and (–)‐isomers also reduced the rate of the atrial pacemaker. Practolol shortened ODI and increased the rate of the atrial and ventricular pacemakers. 3 The (+)‐ and (–)‐isomers were more potent than the racemate; the (–)‐isomer was more potent than the (+)‐isomer. The results suggest there is a stereospecific mechanism involved in the biological distribution of propranolol. 4 Twenty‐four hours after reserpine treatment (5 mg/kg, i.p.) practolol continued to increase the rate of the atrial and ventricular pacemakers but did not shorten ODI. 5 The mechanism by which these agents affect myocardial excitability and automaticity is discussed.