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Effect of transverse gap-junction channels on transverse propagation in an enlarged PSpice model of cardiac muscle

BACKGROUND: In previous PSpice modeling studies of simulated action potentials (APs) in parallel chains of cardiac muscle, it was found that transverse propagation could occur between adjacent chains in the absence of gap-junction (gj) channels, presumably by the electric field (EF) generated in the...

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Autores principales: Ramasamy, Lakshminarayanan, Sperelakis, Nicholas
Formato: Texto
Lenguaje:English
Publicado: BioMed Central 2006
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1440307/
https://www.ncbi.nlm.nih.gov/pubmed/16542447
http://dx.doi.org/10.1186/1742-4682-3-14
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author Ramasamy, Lakshminarayanan
Sperelakis, Nicholas
author_facet Ramasamy, Lakshminarayanan
Sperelakis, Nicholas
author_sort Ramasamy, Lakshminarayanan
collection PubMed
description BACKGROUND: In previous PSpice modeling studies of simulated action potentials (APs) in parallel chains of cardiac muscle, it was found that transverse propagation could occur between adjacent chains in the absence of gap-junction (gj) channels, presumably by the electric field (EF) generated in the narrow interstitial space between the chains. Transverse propagation was sometimes erratic, the more distal chains firing out of order. METHODS: In the present study, the propagation of complete APs was studied in a 2-dimensional network of 100 cardiac muscle cells (10 × 10 model). Various numbers of gj-channels (assumed to be 100 pS each) were inserted across the junctions between the longitudinal cells of each chain and between adjacent chains (only at the end cells of each chain). The shunt resistance produced by the gj-channels (R(gj)) was varied from 100,000 MΩ (0 gj-channels) to 1,000 MΩ (10 channels), 100 MΩ (100 channels) and 10 MΩ (1,000 channels). Total propagation time (TPT) was measured as the difference between the times when the AP rising phase of the first cell (cell # A1) and the last cell (in the J chain) crossed 0 mV. When there were no gj-channels, the excitation was transmitted between cells by the EF, i.e., the negative potential generated in the narrow junctional clefts (e.g., 100 Å) when the prejunctional membrane fired an AP. For the EF mechanism to work, the prejunctional membrane must fire a fraction of a millisecond before the adjacent surface membrane. When there were many gj-channels (e.g., 100 or 1,000), the excitation was transmitted by local-circuit current flow from one cell to the next through these channels. RESULTS: TPT was measured as a function of four different numbers of transverse gj-channels, namely 0, 10, 100 and 1,000, and four different numbers of longitudinal gj-channels, namely 0, 10, 100 and 1,000. Thus, 16 different measurements were made. It was found that increasing the number of transverse channels had no effect on TPT when the number of longitudinal channels was low (i.e., 0 or 10). In contrast, when the number of longitudinal gj-channels was high (e.g., 100 or 1,000), then increasing the number of transverse channels decreased TPT markedly. CONCLUSION: Thus, complete APs could propagate along a network of 100 cardiac muscle cells even when no gj-channels were present between the cells. Insertion of transverse gj-channels greatly speeded propagation through the 10 × 10 network when there were also many longitudinal gj-channels.
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spelling pubmed-14403072006-04-18 Effect of transverse gap-junction channels on transverse propagation in an enlarged PSpice model of cardiac muscle Ramasamy, Lakshminarayanan Sperelakis, Nicholas Theor Biol Med Model Research BACKGROUND: In previous PSpice modeling studies of simulated action potentials (APs) in parallel chains of cardiac muscle, it was found that transverse propagation could occur between adjacent chains in the absence of gap-junction (gj) channels, presumably by the electric field (EF) generated in the narrow interstitial space between the chains. Transverse propagation was sometimes erratic, the more distal chains firing out of order. METHODS: In the present study, the propagation of complete APs was studied in a 2-dimensional network of 100 cardiac muscle cells (10 × 10 model). Various numbers of gj-channels (assumed to be 100 pS each) were inserted across the junctions between the longitudinal cells of each chain and between adjacent chains (only at the end cells of each chain). The shunt resistance produced by the gj-channels (R(gj)) was varied from 100,000 MΩ (0 gj-channels) to 1,000 MΩ (10 channels), 100 MΩ (100 channels) and 10 MΩ (1,000 channels). Total propagation time (TPT) was measured as the difference between the times when the AP rising phase of the first cell (cell # A1) and the last cell (in the J chain) crossed 0 mV. When there were no gj-channels, the excitation was transmitted between cells by the EF, i.e., the negative potential generated in the narrow junctional clefts (e.g., 100 Å) when the prejunctional membrane fired an AP. For the EF mechanism to work, the prejunctional membrane must fire a fraction of a millisecond before the adjacent surface membrane. When there were many gj-channels (e.g., 100 or 1,000), the excitation was transmitted by local-circuit current flow from one cell to the next through these channels. RESULTS: TPT was measured as a function of four different numbers of transverse gj-channels, namely 0, 10, 100 and 1,000, and four different numbers of longitudinal gj-channels, namely 0, 10, 100 and 1,000. Thus, 16 different measurements were made. It was found that increasing the number of transverse channels had no effect on TPT when the number of longitudinal channels was low (i.e., 0 or 10). In contrast, when the number of longitudinal gj-channels was high (e.g., 100 or 1,000), then increasing the number of transverse channels decreased TPT markedly. CONCLUSION: Thus, complete APs could propagate along a network of 100 cardiac muscle cells even when no gj-channels were present between the cells. Insertion of transverse gj-channels greatly speeded propagation through the 10 × 10 network when there were also many longitudinal gj-channels. BioMed Central 2006-03-16 /pmc/articles/PMC1440307/ /pubmed/16542447 http://dx.doi.org/10.1186/1742-4682-3-14 Text en Copyright © 2006 Ramasamy and Sperelakis; licensee BioMed Central Ltd. http://creativecommons.org/licenses/by/2.0 This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( (http://creativecommons.org/licenses/by/2.0) ), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
spellingShingle Research
Ramasamy, Lakshminarayanan
Sperelakis, Nicholas
Effect of transverse gap-junction channels on transverse propagation in an enlarged PSpice model of cardiac muscle
title Effect of transverse gap-junction channels on transverse propagation in an enlarged PSpice model of cardiac muscle
title_full Effect of transverse gap-junction channels on transverse propagation in an enlarged PSpice model of cardiac muscle
title_fullStr Effect of transverse gap-junction channels on transverse propagation in an enlarged PSpice model of cardiac muscle
title_full_unstemmed Effect of transverse gap-junction channels on transverse propagation in an enlarged PSpice model of cardiac muscle
title_short Effect of transverse gap-junction channels on transverse propagation in an enlarged PSpice model of cardiac muscle
title_sort effect of transverse gap-junction channels on transverse propagation in an enlarged pspice model of cardiac muscle
topic Research
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1440307/
https://www.ncbi.nlm.nih.gov/pubmed/16542447
http://dx.doi.org/10.1186/1742-4682-3-14
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