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Comment
. 2010 Apr;48(4):804-6.
doi: 10.1016/j.yjmcc.2009.12.009. Epub 2009 Dec 28.

Funny current provides a relatively modest contribution to spontaneous beating rate regulation of human and rabbit sinoatrial node cells

Victor A Maltsev, Edward G Lakatta
Comment

Funny current provides a relatively modest contribution to spontaneous beating rate regulation of human and rabbit sinoatrial node cells

Victor A Maltsev et al. J Mol Cell Cardiol. 2010 Apr.
No abstract available

Keywords: Na+/Ca2+ exchange current; action potentials; ion channels HCN4 hyperpolarization-activated current; pacemaker activity; sinoatrial node.

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Figures

Figure 1
Figure 1
Steady state activation and kinetics of activation of If in rabbit and humans. Data from isolated human SANC are shown as filled squares and the associated fits as solid lines. (A) Steady-state activation curve. (B) Time constant of (de)activation. The figure is reproduced from [13] with permission. Citation numbers (marked by*) in the figure are those in the original publication[13].
Figure 2
Figure 2
A: Experimentally recorded APs of a single rabbit SANC (top) (numerically reproduced from Fig.1A of the Verkerk and Wilders Letter), associated net membrane current density derived from dVm/dt (Inet, red line, bottom), and numerically reconstructed ion currents (bottom panel, different colors) in rabbit SANC. The currents were simulated by a most recent numerical model of rabbit SANC [5] when all formulations of the model (including Ca2+ cycling) were numerically entrained by voltage clamp using the AP recording in Fig.1A of the Verkerk and Wilders Letter. Maximum conductance of If current was increased to 0.23625 nS/pF in order to reproduce 24 pA/pF If current at –130 mV as in the Verkerk and Wilders Letter. The predicted diastolic increase of INCX (magenta) was caused by the late diastolic Ca2+ elevation in the submembrane space produced by diastolic Ca2+ release from juntional SR in the model (not shown). B: Linescan image of Ca2+ release with superimposed simultaneous AP records during rapid, brief superfusion in the diastolic period with a solution in which Na+ was replaced by Li+. Note that the maneuver blocked the subsequent AP firing by substantially retarding the DD. Red curve superimposed on the last AP preceding spritz of Na+ free solution (in the AP trace, zoomed in right inset) is a copy of the residual membrane potential oscillation observed during the Na+ free solution spritz. Scanned line was oriented perpendicular to long cell axis at half its depth (top inset). From [10].
See this image and copyright information in PMC

Comment on

References

    1. Verkerk AO, Wilders R. Relative importance of funny current in human versus rabbit sinoatrial node. Journal of Molecular and Cellular Cardiology. 2009 in press. - PubMed
    1. Yanagihara K, Irisawa H. Inward current activated during hyperpolarization in the rabbit sinoatrial node cell. Pflugers Arch. 1980;385:11–9. - PubMed
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    1. Maltsev VA, Lakatta EG. Synergism of coupled subsarcolemmal Ca2+ clocks and sarcolemmal voltage clocks confers robust and flexible pacemaker function in a novel pacemaker cell model. Am J Physiol Heart Circ Physiol. 2009;296:H594–H615. - PMC - PubMed