Effects of the beta-adrenergic blocking agents propranolol and timolol on canine cardiac refractory periods

European Journal of Pharmacology
P JaillonG Cheymol


The effects of d,1-propranolol and 1-timolol on cardiac refractory periods (RP) were compared in 14 phentobarbital-anesthetized dogs using endocavitary His bundle electrograms and programmable electrical stimulation. Beta-blocking agents were injected at cumulative doses in each dog at 3 day intervals. A control group (6 dogs) received 4 successive saline injections at the same time intervals. RP measurements at a constant drive rate were done before and 10 minutes after each dose of either drug or saline. Propranolol and timolol produced a dose-dependent increase of atrial and atrioventricular nodal refractory periods; dose-response curves were parallel. Depending on the parameter chosen timolol exerted an 8--36 times more potent effect than propranolol. The effects of propanolol and timolol on ventricular effective (VERP) and functional (VFRP) RP were measured in 6 dogs. Both drugs increased VFRP significantly, but saline had the same effect. Only the higher doses of timolol increased VERP significantly. These data confirm that blockade of myocardial beta-adrenergic receptors exerts predominant effects on supraventricular refractoriness and that in anesthetized dogs timolol has more potent beta-blocking properties than does p...Continue Reading


Feb 1, 1976·European Journal of Pharmacology·P MouilléE Gauter
Apr 1, 1975·European Journal of Pharmacology·J F GiudicelliJ R Boissier
Jan 15, 1978·European Journal of Pharmacology·P JaillonG Cheymol
Jan 1, 1971·Naunyn-Schmiedebergs Archiv Für Pharmakologie·G Zetler, O Strubelt
Dec 1, 1974·American Heart Journal·S F SeidesA N Damato
Dec 1, 1972·The American Journal of Cardiology·K M RosenS H Rahimtoola
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Related Concepts

Refractory Period, Electrophysiological
Nerve Conduction Function
Body Surface Area Formula for Dogs
Beta-adrenergic receptor
Cardiac Conduction System
Structure of Atrioventricular Node
NODAL gene

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