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Potassium and the Excitability Properties of Normal Human Motor Axons In Vivo
Hyperkalemia is an important cause of membrane depolarization in renal failure. A recent theoretical model of axonal excitability explains the effects of potassium on threshold electrotonus, but predicts changes in superexcitability in the opposite direction to those observed. To resolve this contra...
Autores principales: | , , , |
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Formato: | Online Artículo Texto |
Lenguaje: | English |
Publicado: |
Public Library of Science
2014
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Materias: | |
Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4043986/ https://www.ncbi.nlm.nih.gov/pubmed/24893161 http://dx.doi.org/10.1371/journal.pone.0098262 |
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author | Boërio, Delphine Bostock, Hugh Spescha, Romana Z'Graggen, Werner J. |
author_facet | Boërio, Delphine Bostock, Hugh Spescha, Romana Z'Graggen, Werner J. |
author_sort | Boërio, Delphine |
collection | PubMed |
description | Hyperkalemia is an important cause of membrane depolarization in renal failure. A recent theoretical model of axonal excitability explains the effects of potassium on threshold electrotonus, but predicts changes in superexcitability in the opposite direction to those observed. To resolve this contradiction we assessed the relationship between serum potassium and motor axon excitability properties in 38 volunteers with normal potassium levels. Most threshold electrotonus measures were strongly correlated with potassium, and superexcitability decreased at higher potassium levels (P = 0.016), contrary to the existing model. Improved modelling of potassium effects was achieved by making the potassium currents obey the constant-field theory, and by making the potassium permeabilities proportional to external potassium, as has been observed in vitro. This new model also accounted well for the changes in superexcitability and other excitability measures previously reported in renal failure. These results demonstrate the importance of taking potassium levels into account when assessing axonal membrane dysfunction by excitability testing, and provide evidence that potassium currents are activated by external potassium in vivo. |
format | Online Article Text |
id | pubmed-4043986 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2014 |
publisher | Public Library of Science |
record_format | MEDLINE/PubMed |
spelling | pubmed-40439862014-06-09 Potassium and the Excitability Properties of Normal Human Motor Axons In Vivo Boërio, Delphine Bostock, Hugh Spescha, Romana Z'Graggen, Werner J. PLoS One Research Article Hyperkalemia is an important cause of membrane depolarization in renal failure. A recent theoretical model of axonal excitability explains the effects of potassium on threshold electrotonus, but predicts changes in superexcitability in the opposite direction to those observed. To resolve this contradiction we assessed the relationship between serum potassium and motor axon excitability properties in 38 volunteers with normal potassium levels. Most threshold electrotonus measures were strongly correlated with potassium, and superexcitability decreased at higher potassium levels (P = 0.016), contrary to the existing model. Improved modelling of potassium effects was achieved by making the potassium currents obey the constant-field theory, and by making the potassium permeabilities proportional to external potassium, as has been observed in vitro. This new model also accounted well for the changes in superexcitability and other excitability measures previously reported in renal failure. These results demonstrate the importance of taking potassium levels into account when assessing axonal membrane dysfunction by excitability testing, and provide evidence that potassium currents are activated by external potassium in vivo. Public Library of Science 2014-06-03 /pmc/articles/PMC4043986/ /pubmed/24893161 http://dx.doi.org/10.1371/journal.pone.0098262 Text en © 2014 Boërio et al http://creativecommons.org/licenses/by/4.0/ This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are properly credited. |
spellingShingle | Research Article Boërio, Delphine Bostock, Hugh Spescha, Romana Z'Graggen, Werner J. Potassium and the Excitability Properties of Normal Human Motor Axons In Vivo |
title | Potassium and the Excitability Properties of Normal Human Motor Axons In Vivo
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title_full | Potassium and the Excitability Properties of Normal Human Motor Axons In Vivo
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title_fullStr | Potassium and the Excitability Properties of Normal Human Motor Axons In Vivo
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title_full_unstemmed | Potassium and the Excitability Properties of Normal Human Motor Axons In Vivo
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title_short | Potassium and the Excitability Properties of Normal Human Motor Axons In Vivo
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title_sort | potassium and the excitability properties of normal human motor axons in vivo |
topic | Research Article |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4043986/ https://www.ncbi.nlm.nih.gov/pubmed/24893161 http://dx.doi.org/10.1371/journal.pone.0098262 |
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