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Pacemaker synchronization of electrically coupled rabbit sinoatrial node cells.

Verheijck EE, Wilders R, Joyner RW, Golod DA, Kumar R, Jongsma HJ, Bouman LN, van Ginneken AC - J. Gen. Physiol. (1998)

Bottom Line: As the coupling conductance is progressively increased, the cells exhibit: (a) independent pacemaking at low coupling conductances, (b) complex dynamics of activity with mutual interactions, (c) entrainment of action potential frequency at a 1:1 ratio with different action potential waveforms, and (d) entrainment of action potentials at the same frequency of activation and virtually identical action potential waveforms.The critical value of coupling conductance required for 1:1 frequency entrainment was <0.5 nS in each of the five cell pairs studied.At high coupling conductances, the tonic, diastolic interactions become more important.

View Article: PubMed Central - PubMed

Affiliation: Academic Medical Center, University of Amsterdam, Department of Physiology, 1100 DE Amsterdam, The Netherlands. e.verheijck@amc.uva.nl

ABSTRACT
The effects of intercellular coupling conductance on the activity of two electrically coupled isolated rabbit sinoatrial nodal cells were investigated. A computer-controlled version of the "coupling clamp" technique was used in which isolated sinoatrial nodal cells, not physically in contact with each other, were electrically coupled at various values of ohmic coupling conductance, mimicking the effects of mutual interaction by electrical coupling through gap junctional channels. We demonstrate the existence of four types of electrical behavior of coupled spontaneously active cells. As the coupling conductance is progressively increased, the cells exhibit: (a) independent pacemaking at low coupling conductances, (b) complex dynamics of activity with mutual interactions, (c) entrainment of action potential frequency at a 1:1 ratio with different action potential waveforms, and (d) entrainment of action potentials at the same frequency of activation and virtually identical action potential waveforms. The critical value of coupling conductance required for 1:1 frequency entrainment was <0.5 nS in each of the five cell pairs studied. The common interbeat interval at a relatively high coupling conductance (10 nS), which is sufficient to produce entrainment of frequency and also identical action potential waveforms, is determined most by the intrinsically faster pacemaker cell and it can be predicted from the diastolic depolarization times of both cells. Evidence is provided that, at low coupling conductances, mutual pacemaker synchronization results mainly from the phase-resetting effects of the action potential of one cell on the depolarization phase of the other. At high coupling conductances, the tonic, diastolic interactions become more important.

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Simultaneous recording for 10 s of two isolated sinoatrial node cells, with the cells uncoupled during the first and last 2 s and coupled with a coupling conductance of 0.20 nS during the central 6 s. (A) Membrane potential (Vm) of cell A (solid line) and cell B (dotted line), and coupling current (Ic). (B) Data in A replotted for the time period indicated by the horizontal two headed arrow in A. Data from experiment 950803-2 (see Tables).
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Figure 4: Simultaneous recording for 10 s of two isolated sinoatrial node cells, with the cells uncoupled during the first and last 2 s and coupled with a coupling conductance of 0.20 nS during the central 6 s. (A) Membrane potential (Vm) of cell A (solid line) and cell B (dotted line), and coupling current (Ic). (B) Data in A replotted for the time period indicated by the horizontal two headed arrow in A. Data from experiment 950803-2 (see Tables).

Mentions: Figs. 3–5 show data from the same cell pair in the same presentation format as for Fig. 2, using values of coupling conductance of 0.15 nS (Fig. 3), 0.20 nS (Fig. 4), and 10 nS (Fig. 5). For the period of coupling illustrated in Fig. 3, each of the action potentials (numbered 1–17) for cell A occur before an associated action potential of cell B, except action potentials numbered 8 and 9. For these two action potentials, the process described for Fig. 2 occurs, in which action potential number 8 of cell A produces a subthreshold depolarization during the diastolic period of cell B and this depolarization in cell B delays the subsequent activation of cell B. This subsequent activation of cell B occurs before action potential number 9 of cell A (Fig. 3A, arrow), but action potential number 10 of cell A reestablishes the pattern of the action potential of cell A occurring before the associated action potential of cell B. Note that, at this higher value of coupling conductance (0.15 nS), this process occurs only once during the coupling period, as compared with the three occurrences during the coupling period when the coupling conductance was 0.1 nS (Fig. 2).


Pacemaker synchronization of electrically coupled rabbit sinoatrial node cells.

Verheijck EE, Wilders R, Joyner RW, Golod DA, Kumar R, Jongsma HJ, Bouman LN, van Ginneken AC - J. Gen. Physiol. (1998)

Simultaneous recording for 10 s of two isolated sinoatrial node cells, with the cells uncoupled during the first and last 2 s and coupled with a coupling conductance of 0.20 nS during the central 6 s. (A) Membrane potential (Vm) of cell A (solid line) and cell B (dotted line), and coupling current (Ic). (B) Data in A replotted for the time period indicated by the horizontal two headed arrow in A. Data from experiment 950803-2 (see Tables).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC1887765&req=5

Figure 4: Simultaneous recording for 10 s of two isolated sinoatrial node cells, with the cells uncoupled during the first and last 2 s and coupled with a coupling conductance of 0.20 nS during the central 6 s. (A) Membrane potential (Vm) of cell A (solid line) and cell B (dotted line), and coupling current (Ic). (B) Data in A replotted for the time period indicated by the horizontal two headed arrow in A. Data from experiment 950803-2 (see Tables).
Mentions: Figs. 3–5 show data from the same cell pair in the same presentation format as for Fig. 2, using values of coupling conductance of 0.15 nS (Fig. 3), 0.20 nS (Fig. 4), and 10 nS (Fig. 5). For the period of coupling illustrated in Fig. 3, each of the action potentials (numbered 1–17) for cell A occur before an associated action potential of cell B, except action potentials numbered 8 and 9. For these two action potentials, the process described for Fig. 2 occurs, in which action potential number 8 of cell A produces a subthreshold depolarization during the diastolic period of cell B and this depolarization in cell B delays the subsequent activation of cell B. This subsequent activation of cell B occurs before action potential number 9 of cell A (Fig. 3A, arrow), but action potential number 10 of cell A reestablishes the pattern of the action potential of cell A occurring before the associated action potential of cell B. Note that, at this higher value of coupling conductance (0.15 nS), this process occurs only once during the coupling period, as compared with the three occurrences during the coupling period when the coupling conductance was 0.1 nS (Fig. 2).

Bottom Line: As the coupling conductance is progressively increased, the cells exhibit: (a) independent pacemaking at low coupling conductances, (b) complex dynamics of activity with mutual interactions, (c) entrainment of action potential frequency at a 1:1 ratio with different action potential waveforms, and (d) entrainment of action potentials at the same frequency of activation and virtually identical action potential waveforms.The critical value of coupling conductance required for 1:1 frequency entrainment was <0.5 nS in each of the five cell pairs studied.At high coupling conductances, the tonic, diastolic interactions become more important.

View Article: PubMed Central - PubMed

Affiliation: Academic Medical Center, University of Amsterdam, Department of Physiology, 1100 DE Amsterdam, The Netherlands. e.verheijck@amc.uva.nl

ABSTRACT
The effects of intercellular coupling conductance on the activity of two electrically coupled isolated rabbit sinoatrial nodal cells were investigated. A computer-controlled version of the "coupling clamp" technique was used in which isolated sinoatrial nodal cells, not physically in contact with each other, were electrically coupled at various values of ohmic coupling conductance, mimicking the effects of mutual interaction by electrical coupling through gap junctional channels. We demonstrate the existence of four types of electrical behavior of coupled spontaneously active cells. As the coupling conductance is progressively increased, the cells exhibit: (a) independent pacemaking at low coupling conductances, (b) complex dynamics of activity with mutual interactions, (c) entrainment of action potential frequency at a 1:1 ratio with different action potential waveforms, and (d) entrainment of action potentials at the same frequency of activation and virtually identical action potential waveforms. The critical value of coupling conductance required for 1:1 frequency entrainment was <0.5 nS in each of the five cell pairs studied. The common interbeat interval at a relatively high coupling conductance (10 nS), which is sufficient to produce entrainment of frequency and also identical action potential waveforms, is determined most by the intrinsically faster pacemaker cell and it can be predicted from the diastolic depolarization times of both cells. Evidence is provided that, at low coupling conductances, mutual pacemaker synchronization results mainly from the phase-resetting effects of the action potential of one cell on the depolarization phase of the other. At high coupling conductances, the tonic, diastolic interactions become more important.

Show MeSH
Related in: MedlinePlus