AJP - Heart and Circulatory Physiology, Vol 273, Issue 2 767-H776, Copyright © 1997 by American Physiological Society

ARTICLES

Electrotonic modulation of electrical activity in rabbit atrioventricular node myocytes

K. W. Spitzer, N. Sato, H. Tanaka, L. Firek, M. Zaniboni and W. R. Giles
Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, Salt Lake City 84112, USA.

Electrotonic effects of electrically coupling atrioventricular (AV) nodal cells to each other and to real and passive models of atrial and ventricular cells were studied using a technique that does not require functional gap junctions. Membrane potential was measured in each cell using suction pipettes. Mutual entrainment of two spontaneously firing AV nodal cells was achieved with a junctional resistance (Rj) of 500 M omega, which corresponds to only 39 junctional channels, assuming a single-channel conductance of 50 pS. Coupling of AV nodal and atrial cells at Rj of 50 M omega caused hyperpolarization of the nodal cell, decreasing its action potential duration and either slowing or blocking diastolic depolarization in the AV node myocyte. Opposite changes occurred in the atrial action potential. When AV nodal and ventricular cells were coupled at Rj of 50 M omega, nodal diastolic potential was markedly hyperpolarized and diastolic depolarization was completely blocked with little change in ventricular diastolic potential. However, coupling did elicit marked changes in the action potential duration of both cells, with prolongation in the nodal cell and shortening in the ventricular cell. Nodal maximum upstroke velocity was increased by both atrial and ventricular coupling, as expected from the hyperpolarization that occurred. With an Rj of 50 M omega, spontaneous firing was blocked in all single AV nodal pacemaker cells during coupling to a real or passive model of an atrial or ventricular cell. These results demonstrate that action potential formation and waveform in a single AV nodal cell is significantly affected by electrical coupling to other myocytes.

This article has been cited by other articles:

				V. E. Bondarenko and R. L. Rasmusson Simulations of propagated mouse ventricular action potentials: effects of molecular heterogeneity Am J Physiol Heart Circ Physiol, September 1, 2007; 293(3): H1816 - H1832. [Abstract] [Full Text] [PDF]

				K. J. Sampson and C. S. Henriquez Electrotonic influences on action potential duration dispersion in small hearts: a simulation study Am J Physiol Heart Circ Physiol, July 1, 2005; 289(1): H350 - H360. [Abstract] [Full Text] [PDF]

				R. W. Joyner, Y.-G. Wang, R. Wilders, D. A. Golod, M. B. Wagner, R. Kumar, and W. N. Goolsby A spontaneously active focus drives a model atrial sheet more easily than a model ventricular sheet Am J Physiol Heart Circ Physiol, August 1, 2000; 279(2): H752 - H763. [Abstract] [Full Text] [PDF]

				M. Zaniboni, A. E. Pollard, L. Yang, and K. W. Spitzer Beat-to-beat repolarization variability in ventricular myocytes and its suppression by electrical coupling Am J Physiol Heart Circ Physiol, March 1, 2000; 278(3): H677 - H687. [Abstract] [Full Text] [PDF]

				M. B. Wagner, T. Namiki, R. Wilders, R. W. Joyner, H. J. Jongsma, E. E. Verheijck, R. Kumar, D. A. Golod, W. N. Goolsby, and A. C. G. van Ginneken Electrical interactions among real cardiac cells and cell models in a linear strand Am J Physiol Heart Circ Physiol, February 1, 1999; 276(2): H391 - H400. [Abstract] [Full Text] [PDF]

				D. J. Huelsing, K. W. Spitzer, J. M. Cordeiro, and A. E. Pollard Modulation of repolarization in rabbit Purkinje and ventricular myocytes coupled by a variable resistance Am J Physiol Heart Circ Physiol, February 1, 1999; 276(2): H572 - H581. [Abstract] [Full Text] [PDF]

				R. W. Joyner, R. Kumar, D. A. Golod, R. Wilders, H. J. Jongsma, E. E. Verheijck, L. Bouman, W. N. Goolsby, and A. C. G. Van Ginneken Electrical interactions between a rabbit atrial cell and a nodal cell model Am J Physiol Heart Circ Physiol, June 1, 1998; 274(6): H2152 - H2162. [Abstract] [Full Text] [PDF]