1980 年 132 巻 3 号 p. 245-259
Effects of ouabain on atrioventricular (AV) conduction were studied by using the canine excised, blood-perfused AV node preparations. Ouabain was continuously infused either selectively into the AV node artery (I) or systemically i. v. into the pentobarbital-anesthetized (II) and the pithed donor dog (III). AV conduction in the isolated AV node preparation was interrupted by AV block in the half of I and II and in all of III after prominent prolongation of AV conduction time. In the remaining half of I and II, AV conduction was interrupted by accelerated prematures. The prematures continued to increase. After AV block ventricular rate decreased in the half of I and II and the inherent automaticity was sustained in all of III. PQ interval of the donor dog was interrupted by accelerated prematures in all of II and two thirds of III. In one third of III, AV block was induced. Interrupting doses of ouabain in the isolated AV node preparation of II and III and in the pithed donor dog heart were almost similar, all of which were significantly larger than that in pentobarbital-anesthetized dog heart. It is concluded that ouabain depresses directly AV conduction but this effect was modified by sympathetic nerve activity in the nerve-intact animals and also by inherent characteristics of the AV nodal cells.
