Resting and Action Potentials in the Region of the Atrioventricular Node

Abstract

The resting and action potentials in the region of the atrioventricular node were studied by the intracellular microelectrode method. The action potential here had a characteristic configuration. Different from that in other regions it had a step-like part at the beginning of its rising limb. Resting potential, action potential, and overshoot were all remarkably smaller than those in other regions. The average resting potential, action potential, and overshoot were 53, 58, and 5mV respectively. The spot where such characteristic action potential was obtained had a very limited extension, about 1mm in size. It was histologically confirmed that this action potential originated actually from the cells of the special junctional tissue. When this region gained spontaneous activity, slow diastolic depolarization was observed. When l-noradrenaline was added to the Tyrode solution, the rate of rise of the step was increased, the duration of the step shortened, and other parts of the action potential advanced. Procaine amide, quinidine, and digitalis glycosides had opposite effects, resulting in retroceding of the chief parts of the action potential. These changes were completely reversible.