Effects of verapamil on SA and AV nodal action potentials in the isolated rabbit heart.

In the isolated rabbit heart, it was shown that verapamil suppressed the electrical activities of the SA and AV nodes without preventing regenerative responses in atrial muscle fibers. It was concluded that the different effects of verapamil on SA and AV nodal action potentials resulted from the operation of a different ionic channel (slow channel) from that of ordinary atrial muscle.