Effects on A-V Conduction of Tetrodotoxin Selectively Injected into the A-V Node Artery of the Dog

Abstract

Tetrodotoxin was injected selectively into the A-V node artery of the dog heart in situ, of which both vagi and both cardiac nerves were cut. Tetrodotoxin at doses of 1 to 3 μg abolished effects of electrical stimulation of either the left vagus or the left cardiac nerve on A-V conduction without any direct effect on A-V conduction. A very large dose of tetrodotoxin decelerated A-V conduction. These results led to the conclusion that cells concerned with major part of the A-V delay was less affected by tetrodotoxin than the autonomic nerve fibers that cause decisive effect on A-V conduction.