Effects of cardioactive substances on the post-stimulation potentiation of contractility in the isolated dog atrium.

Effects of cardioactive substances on the post-stimulation potentiation of atrial contractility were studied in 17 isolated, blood-perfused preparations of dogs. Maximum degree of the post-stimulation potentiation was obtained over approximately 3.5 Hz within 5-60 sec of stimulation. Each drug was administered directly into the cannulated sinus node artery of isolated atrium. An adequate dose of verapramil, manganese chloride, or pentobarbital which caused marked depression of contractility did not significantly suppress the post-stimulation potentiation in percent changes. The post-stimulation potentiation was not inhibited by continuous infusion of adenosine, which caused a negative inotropic effect. Tetrodotoxin, propranolol, or caffeine also never suppressed the post-stimulation potentiation but ouabain abolished it in the majority of cases.