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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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Interbeat interval (IBI) for cells A and B (top, • and □, respectively) and the delay in activation of cell B with respect to the activation of cell A (bottom, ▴) for a coupling conductance Gc (horizontal arrow). (A) Gc = 0.2 nS. (B) Gc = 10 nS. The data in A and B come from the action potential recordings of Figs. 4 and 5, respectively. Data from experiment 950803-2 (see Tables).
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Figure 7: Interbeat interval (IBI) for cells A and B (top, • and □, respectively) and the delay in activation of cell B with respect to the activation of cell A (bottom, ▴) for a coupling conductance Gc (horizontal arrow). (A) Gc = 0.2 nS. (B) Gc = 10 nS. The data in A and B come from the action potential recordings of Figs. 4 and 5, respectively. Data from experiment 950803-2 (see Tables).

Mentions: Fig. 2 shows simultaneous recordings from two SA nodal cells, with the membrane potential recordings of the two cells distinguished by a solid (for cell A) or dotted (for cell B) line. Data for Fig. 2, as well as Figs. 3–7, are from experiment 950803-2 (Table II). Fig. 2A (top) shows the experimental protocol in which the recordings were made without electrical coupling between the cells for two seconds, followed by a period of 6 s of electrical coupling at 0.10 nS, and then by a second period of uncoupling for 2 s. During the periods of uncoupling, the spontaneous activity of cell A is occurring at a shorter interbeat interval (310 ms) than the spontaneous activity of cell B (390 ms). The action potentials of the two cells are also somewhat different in shape, with cell A having a less negative maximum diastolic potential (−57 vs. −62 mV) and a less positive peak amplitude (26 vs. 28 mV) than cell B. Cell A also has a shorter action potential duration than cell B. The measured action potential parameters for these cells, when uncoupled, are listed in Table I, along with the parameter values for the cells of the other four cell pairs from which recordings were made. The Fig. 2A (bottom) plots the coupling current for this cell pair. The coupling current is, of course, zero during the two periods of uncoupling, and is plotted as a positive current in the direction from cell A to cell B.


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)

Interbeat interval (IBI) for cells A and B (top, • and □, respectively) and the delay in activation of cell B with respect to the activation of cell A (bottom, ▴) for a coupling conductance Gc (horizontal arrow). (A) Gc = 0.2 nS. (B) Gc = 10 nS. The data in A and B come from the action potential recordings of Figs. 4 and 5, respectively. Data from experiment 950803-2 (see Tables).
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Related In: Results  -  Collection

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Figure 7: Interbeat interval (IBI) for cells A and B (top, • and □, respectively) and the delay in activation of cell B with respect to the activation of cell A (bottom, ▴) for a coupling conductance Gc (horizontal arrow). (A) Gc = 0.2 nS. (B) Gc = 10 nS. The data in A and B come from the action potential recordings of Figs. 4 and 5, respectively. Data from experiment 950803-2 (see Tables).
Mentions: Fig. 2 shows simultaneous recordings from two SA nodal cells, with the membrane potential recordings of the two cells distinguished by a solid (for cell A) or dotted (for cell B) line. Data for Fig. 2, as well as Figs. 3–7, are from experiment 950803-2 (Table II). Fig. 2A (top) shows the experimental protocol in which the recordings were made without electrical coupling between the cells for two seconds, followed by a period of 6 s of electrical coupling at 0.10 nS, and then by a second period of uncoupling for 2 s. During the periods of uncoupling, the spontaneous activity of cell A is occurring at a shorter interbeat interval (310 ms) than the spontaneous activity of cell B (390 ms). The action potentials of the two cells are also somewhat different in shape, with cell A having a less negative maximum diastolic potential (−57 vs. −62 mV) and a less positive peak amplitude (26 vs. 28 mV) than cell B. Cell A also has a shorter action potential duration than cell B. The measured action potential parameters for these cells, when uncoupled, are listed in Table I, along with the parameter values for the cells of the other four cell pairs from which recordings were made. The Fig. 2A (bottom) plots the coupling current for this cell pair. The coupling current is, of course, zero during the two periods of uncoupling, and is plotted as a positive current in the direction from cell A to cell B.

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