Action Potential Changes under Varied [Na+]0 and [Ca2+]0 Indicating the Existence of Two Inward Currents in Cells of the Rabbit Atrioventricular Node

In the perfused rabbit heart,the upstroke of the transmembrane action potential of fibers of the atrioventricular (AV) node presents two distinct components. The first depends strongly on extracellular sdoium concentration, but the degree to which it is activated is influenced by extracellular calcium, as indicated by the correlation between its Vmax and [Ca2+]0. The second component depends on calcium and sodium concentrations and is blocked by Mn ions. An analysis comparing action potentials from atrial (A), atrionodal (AN), and nodal (N) fibers shows that the second component of the upstroke of the action potential contributes 12%, 27%, and 34% to the total depolarization. The results suggest that the upstroke of the nodal action potential results from the activation of two inward currents, as in ordinary cardiac fibers. We postulate that (1) the degree of steady state inactivation of gNa is larger in N than in A fibers because of the low resting potential of the former, and (2) the contribution of the second channel to the upstroke depends on the time course of the previous depolarization and the potential level at which this component is activated.

[1]  H. Irisawa,et al.  The effect of polarization on the action potentials of the rabbit AV nodal cells. , 1974, The Japanese journal of physiology.

[2]  A. L. Wit,et al.  Effect of Verapamil on the Sinoatrial and Atrioventricular Nodes of the Rabbit and the Mechanism by Which it Arrests Reentrant Atrioventricular Nodal Tachycardia , 1974, Circulation research.

[3]  R. J. Turner,et al.  Effects of temperature change and adrenaline on sinoatrial and atrioventricular nodal potentials. , 1974, Cardiovascular research.

[4]  E. Reisler,et al.  Myosin ATP hydrolysis: a mechanism involving a magnesium chelate complex. , 1973, Proceedings of the National Academy of Sciences of the United States of America.

[5]  D. Zipes,et al.  Action of Manganese Ions and Tetrodotoxin on Atrioventricular Nodal Transmembrane Potentials in Isolated Rabbit Hearts , 1973, Circulation research.

[6]  J. Alanís,et al.  The electrical activity of the bundle of His , 1958, Pflugers Archiv : European journal of physiology.

[7]  H. Reuter,et al.  Divalent cations as charge carriers in excitable membranes. , 1973, Progress in biophysics and molecular biology.

[8]  P. Pinell,et al.  Effects of thyroid hormones on phosphorylation of liver ribosomal proteins and on protein phosphokinase activity , 1972, FEBS letters.

[9]  M. Tarr.  Two Inward Currents in Frog Atrial Muscle , 1971, The Journal of general physiology.

[10]  A. P. Ponce Zumino,et al.  Resolution of two components in the upstroke of the action potential in atrioventricular fibers of the rabbit heart. , 1971, Canadian journal of physiology and pharmacology.

[11]  S. Perry,et al.  An electrophoretic study of the low-molecular-weight components of myosin. , 1970, The Biochemical journal.

[12]  I. M. Parisii,et al.  Effect of ischemia and low-sodium medium on atrioventricular conduction. , 1970, The American journal of physiology.

[13]  J. Alanís,et al.  Calcium ions and the propagation of impulses through the mammalian heart junctional regions. , 1970, The Japanese journal of physiology.

[14]  G. W. Beeler,et al.  Membrane calcium current in ventricular myocardial fibres , 1970, The Journal of physiology.

[15]  G W Beeler,et al.  Voltage clamp experiments on ventricular myocardial fibres , 1970, The Journal of physiology.

[16]  K. Matsuda,et al.  Contribution of calcium current to the ventricular action potential of dog. , 1969, The Japanese journal of physiology.

[17]  B. Hoffman,et al.  Two Components of the Cardiac Action Potential I. Voltage-time Course and the Effect of Acet.flcholine on Atrial and Nodal Cells of the Rabbit Heart the Journal of General Physiology , 2008 .

[18]  K. Weber,et al.  The reliability of molecular weight determinations by dodecyl sulfate-polyacrylamide gel electrophoresis. , 1969, The Journal of biological chemistry.

[19]  E. Lepeschkin.  Electrophysiology and Ultrastructure of the Heart. , 1969 .

[20]  L. DeFelice,et al.  Anatomical and Ultrastructural Study of the Electrophysiological Atrioventricular Node of the Rabbit , 1969, Circulation research.

[21]  G. Langer.  Ion fluxes in cardiac excitation and contraction and their relation to myocardial contractility. , 1968, Physiological reviews.

[22]  H. Reuter.  Slow inactivation of currents in cardiac Purkinje fibres , 1968, The Journal of physiology.

[23]  永田 俊彌.  An experimental study on the conduction of excitation in the A-V nodal region , 1968 .

[24]  G. Vassort,et al.  Effects of some inhibitors of ionic permeabilities on ventricular action potential and contraction of rat and guinea-pig hearts. , 1968, Journal of electrocardiology.

[25]  H. Reuter,et al.  The dependence of slow inward current in Purkinje fibres on the extracellular calcium‐concentration , 1967, The Journal of physiology.

[26]  M. Calabresi.  Mechanisms and Therapy of Cardiac Arrhythmias , 1967 .

[27]  T. Nagata.  An experimental study on the conduction of excitation in the A-V nodal region. , 1966, Japanese circulation journal.

[28]  T. Kanno,et al.  The Effects of External Sodium and Potassium Concentration on the Membrane Potential of Atrioventricular Fibers of the Toad , 1966, The Journal of general physiology.

[29]  R. Orkand,et al.  The dual effect of calcium on the action potential of the frog's heart , 1966, The Journal of physiology.

[30]  Na,et al.  The Journal of General Physiology , 2022 .

[31]  H. Jenerick,et al.  PHASE PLANE TRAJECTORIES OF THE MUSCLE SPIKE POTENTIAL. , 1963, Biophysical journal.

[32]  R. Stockwell.  The Specialized Tissues of the Heart , 1963 .

[33]  E. Wright,et al.  Action potential of amphibian single auricular muscle fiber: a dual response. , 1961, The American journal of physiology.

[34]  A. de Carvalho,et al.  Spread of Activity Through the Atrioventricular Node , 1960, Circulation research.

[35]  B. Hoffman,et al.  Electrical Activity of Single Fibers of the Atrioventricular Node , 1959, Circulation research.

[36]  A. C. Young,et al.  The Mechanism of Atrioventricular Conduction , 1959, Circulation research.

[37]  A. Hodgkin,et al.  The action of calcium on the electrical properties of squid axons , 1957, The Journal of physiology.

[38]  S. Weidmann,et al.  Effects of calcium ions and local anaesthetics on electrical properties of Purkinje fibres , 1955, The Journal of physiology.

[39]  A. Hodgkin,et al.  A quantitative description of membrane current and its application to conduction and excitation in nerve , 1952, The Journal of physiology.

[40]  A. Hodgkin,et al.  The effect of temperature on the electrical activity of the giant axon of the squid , 1949, The Journal of physiology.

[41]  C. H. Fiske,et al.  THE COLORIMETRIC DETERMINATION OF PHOSPHORUS , 1925 .