Dominant anti-vagal effect of pentobarbital on cardiac responses to intracardiac autonomic nerve stimulation in the dog.

The isolated canine atrium was perfused by heparinized blood of the donor dog. An adequate dose of pentobarbital that induced a potent hypotension in the donor did not produce any significant change in the atrial rate and developed tension in the isolated atrium perfused with donor's blood. Pentobarbital in doses that modified neither cardiac responses to intracardiac adrenergic nerve stimulation nor exogenously given norepinephrine or acetylcholine significantly inhibited intracardiac vagal responses. From these results, it is concluded that a large dose of pentobarbital has a dominant antivagal effect in the heart.