TY - JOUR
T1 - Electrophysiology of functional subsidiary pacemakers in canine right atrium
AU - Rozanski, G. J.
AU - Lipsius, S. L.
N1 - Copyright:
Copyright 2020 Elsevier B.V., All rights reserved.
PY - 1985
Y1 - 1985
N2 - Glass microelectrodes were used to study the electrical activity of the subsidiary atrial pacemaker (SAP) cells that maintain atrial excitation after suppression of the sinoatrial node. Tissues with documented SAP activity were isolated from the canine inferior right atrium and superfused in vitro with Tyrode solution containing norepinephrine (NE, 10-8-10-7 M). SAP action potentials exhibited prominent diastolic depolarization and a significantly lower maximum diastolic potential, take-off potential, overshoot, rate of rise, and amplitude than typical atrial muscle. Withdrawal of NE completely blocked SAP propagation, although SAP automaticity continued at a slower rate. Acetylcholine (ACh, 5 x 10-8 M) usually produced complete exit block and decreased spontaneous rate. Higher concentrations of ACh (10-6 M) elicited a prominent hyperpolarization (19.2 ± 6.6 mV), completely suppressing SAP automaticity. In quiescent preparations exposed to NE ≥10-7 M, external stimuli at short cycle lengths (<1,000 ms) elicited action potentials with delayed afterdepolarizations, which frequently caused nondriven repetitive activity. This triggered activity was inhibited by verapamil or withdrawal of NE. These studies identify and characterize the electrical activity of functional subsidiary pacemakers located in a specific region of the inferior right atrium. In addition, fibers within this region display triggered activity. Spontaneous activity generated by fibers within the SAP region may cause atrial dysrhythmias.
AB - Glass microelectrodes were used to study the electrical activity of the subsidiary atrial pacemaker (SAP) cells that maintain atrial excitation after suppression of the sinoatrial node. Tissues with documented SAP activity were isolated from the canine inferior right atrium and superfused in vitro with Tyrode solution containing norepinephrine (NE, 10-8-10-7 M). SAP action potentials exhibited prominent diastolic depolarization and a significantly lower maximum diastolic potential, take-off potential, overshoot, rate of rise, and amplitude than typical atrial muscle. Withdrawal of NE completely blocked SAP propagation, although SAP automaticity continued at a slower rate. Acetylcholine (ACh, 5 x 10-8 M) usually produced complete exit block and decreased spontaneous rate. Higher concentrations of ACh (10-6 M) elicited a prominent hyperpolarization (19.2 ± 6.6 mV), completely suppressing SAP automaticity. In quiescent preparations exposed to NE ≥10-7 M, external stimuli at short cycle lengths (<1,000 ms) elicited action potentials with delayed afterdepolarizations, which frequently caused nondriven repetitive activity. This triggered activity was inhibited by verapamil or withdrawal of NE. These studies identify and characterize the electrical activity of functional subsidiary pacemakers located in a specific region of the inferior right atrium. In addition, fibers within this region display triggered activity. Spontaneous activity generated by fibers within the SAP region may cause atrial dysrhythmias.
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U2 - 10.1152/ajpheart.1985.249.3.h594
DO - 10.1152/ajpheart.1985.249.3.h594
M3 - Article
C2 - 4037107
AN - SCOPUS:17744404418
VL - 18
SP - H594-H603
JO - American Journal of Physiology - Renal Physiology
JF - American Journal of Physiology - Renal Physiology
SN - 0363-6127
IS - 3
ER -