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Barbiturates Block Sodium and Potassium Conductance Increases in Voltage-Clamped Lobster Axons
Sodium pentobarbital and sodium thiopental decrease both the peak initial (Na) and late steady-state (K) currents and reduce the maximum sodium and potassium conductance increases in voltage-clamped lobster giant axons. These barbiturates also slow the rate at which the sodium conductance turns on,...
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Formato: | Texto |
Lenguaje: | English |
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The Rockefeller University Press
1968
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Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2201133/ https://www.ncbi.nlm.nih.gov/pubmed/5648829 |
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author | Blaustein, M. P. |
author_facet | Blaustein, M. P. |
author_sort | Blaustein, M. P. |
collection | PubMed |
description | Sodium pentobarbital and sodium thiopental decrease both the peak initial (Na) and late steady-state (K) currents and reduce the maximum sodium and potassium conductance increases in voltage-clamped lobster giant axons. These barbiturates also slow the rate at which the sodium conductance turns on, and shift the normalized sodium conductance vs. voltage curves in the direction of depolarization along the voltage axis. Since pentobarbital (pK(a) = 8.0) blocks the action potential more effectively at pH 8.5 than at pH 6.7, the anionic form of the drug appears to be active. The data suggest that these drugs affect the axon membrane directly, rather than secondarily through effects on intermediary metabolism. It is suggested that penetration of the lipid layer of the membrane by the nonpolar portion of the barbiturate molecules may cause the decrease in membrane conductances, while electrostatic interactions involving the anionic group on the barbiturate, divalent cations, and "fixed charges" in the membrane could account for the slowing of the rate of sodium conductance turn-on and the shift of the normalized conductance curves along the voltage axis. |
format | Text |
id | pubmed-2201133 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 1968 |
publisher | The Rockefeller University Press |
record_format | MEDLINE/PubMed |
spelling | pubmed-22011332008-04-23 Barbiturates Block Sodium and Potassium Conductance Increases in Voltage-Clamped Lobster Axons Blaustein, M. P. J Gen Physiol Article Sodium pentobarbital and sodium thiopental decrease both the peak initial (Na) and late steady-state (K) currents and reduce the maximum sodium and potassium conductance increases in voltage-clamped lobster giant axons. These barbiturates also slow the rate at which the sodium conductance turns on, and shift the normalized sodium conductance vs. voltage curves in the direction of depolarization along the voltage axis. Since pentobarbital (pK(a) = 8.0) blocks the action potential more effectively at pH 8.5 than at pH 6.7, the anionic form of the drug appears to be active. The data suggest that these drugs affect the axon membrane directly, rather than secondarily through effects on intermediary metabolism. It is suggested that penetration of the lipid layer of the membrane by the nonpolar portion of the barbiturate molecules may cause the decrease in membrane conductances, while electrostatic interactions involving the anionic group on the barbiturate, divalent cations, and "fixed charges" in the membrane could account for the slowing of the rate of sodium conductance turn-on and the shift of the normalized conductance curves along the voltage axis. The Rockefeller University Press 1968-03-01 /pmc/articles/PMC2201133/ /pubmed/5648829 Text en Copyright © 1968 by The Rockefeller University Press This article is distributed under the terms of an Attribution–Noncommercial–Share Alike–No Mirror Sites license for the first six months after the publication date (see http://www.rupress.org/terms). After six months it is available under a Creative Commons License (Attribution–Noncommercial–Share Alike 4.0 Unported license, as described at http://creativecommons.org/licenses/by-nc-sa/4.0/). |
spellingShingle | Article Blaustein, M. P. Barbiturates Block Sodium and Potassium Conductance Increases in Voltage-Clamped Lobster Axons |
title | Barbiturates Block Sodium and Potassium Conductance Increases in Voltage-Clamped Lobster Axons |
title_full | Barbiturates Block Sodium and Potassium Conductance Increases in Voltage-Clamped Lobster Axons |
title_fullStr | Barbiturates Block Sodium and Potassium Conductance Increases in Voltage-Clamped Lobster Axons |
title_full_unstemmed | Barbiturates Block Sodium and Potassium Conductance Increases in Voltage-Clamped Lobster Axons |
title_short | Barbiturates Block Sodium and Potassium Conductance Increases in Voltage-Clamped Lobster Axons |
title_sort | barbiturates block sodium and potassium conductance increases in voltage-clamped lobster axons |
topic | Article |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2201133/ https://www.ncbi.nlm.nih.gov/pubmed/5648829 |
work_keys_str_mv | AT blausteinmp barbituratesblocksodiumandpotassiumconductanceincreasesinvoltageclampedlobsteraxons |