Vagal and Sympathetic Effects on Membrane Potential of Atrio-ventricular Conducting Fibers of Toads
1963 年 81 巻 1 号 p. 85-92
詳細
1963 年 81 巻 1 号 p. 85-92
The dromotropic action of the cardiac nerve was studied in the toad by observing the change of membrane action potentials of the A-V conducting tissue when the septal nerve was electrically stimulated.
By shifting the microelectrode stepwise along the A-V pathway, three different types of action potentials were observed from the atrial part, the atrial margin, and the middle and ventricular parts of A-V pathway.
Electrical stimulation of the septal nerve had a preferential effect on the membrane action potential of the atrial margin. The upstroke was slowed, the amplitude was diminished and the plateau was shortened. This effect was reversed after atropinization: acceleration of upstroke, increase of amplitude and lengthening of plateau phase.
It is concluded that both negative and positive dromotropic effects of cardiac nerves in this animal are attributable to the special susceptibility of action potential of the atrial margin of the A-V conducting pathway to both vagal and sympathetic transmitters.
