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Evidence for a population of sleepy sodium channels in squid axon at low temperature
We have studied the effects of temperature changes on Na currents in squid giant axons. Decreases in temperature in the 15-1 degrees C range decrease peak Na current with a Q10 of 2.2. Steady state currents, which are tetrodotoxin sensitive and have the same reversal potential as peak currents, are...
Formato: | Texto |
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Lenguaje: | English |
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The Rockefeller University Press
1982
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Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2215509/ https://www.ncbi.nlm.nih.gov/pubmed/6284858 |
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collection | PubMed |
description | We have studied the effects of temperature changes on Na currents in squid giant axons. Decreases in temperature in the 15-1 degrees C range decrease peak Na current with a Q10 of 2.2. Steady state currents, which are tetrodotoxin sensitive and have the same reversal potential as peak currents, are almost unaffected by temperature changes. After removal of inactivation by pronase treatment, steady state current amplitude has a Q10 of 2.3. Na currents generated at large positive voltages sometimes exhibit a biphasic activation pattern. The first phase activates rapidly and partially inactivates and is followed by a secondary slow current increase that lasts several milliseconds. Peak Na current amplitude can be increased by delivering large positive prepulses, an effect that is more pronounced at low temperatures. The slow activation phase is eliminated after a positive prepulse. The results are consistent with the hypothesis that there are two forms of the Na channel: (a) rapidly activating channels that completely inactivate, and (b) slowly activating "sleepy" channels that inactivate slowly if at all. Some fast channels are assumed to be converted to sleepy channels by cooling, possibly because of a phase transition in the membrane. The existence of sleepy channels complicates the determination of the Q10 of gating parameters and single-channel conductance. |
format | Text |
id | pubmed-2215509 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 1982 |
publisher | The Rockefeller University Press |
record_format | MEDLINE/PubMed |
spelling | pubmed-22155092008-04-23 Evidence for a population of sleepy sodium channels in squid axon at low temperature J Gen Physiol Articles We have studied the effects of temperature changes on Na currents in squid giant axons. Decreases in temperature in the 15-1 degrees C range decrease peak Na current with a Q10 of 2.2. Steady state currents, which are tetrodotoxin sensitive and have the same reversal potential as peak currents, are almost unaffected by temperature changes. After removal of inactivation by pronase treatment, steady state current amplitude has a Q10 of 2.3. Na currents generated at large positive voltages sometimes exhibit a biphasic activation pattern. The first phase activates rapidly and partially inactivates and is followed by a secondary slow current increase that lasts several milliseconds. Peak Na current amplitude can be increased by delivering large positive prepulses, an effect that is more pronounced at low temperatures. The slow activation phase is eliminated after a positive prepulse. The results are consistent with the hypothesis that there are two forms of the Na channel: (a) rapidly activating channels that completely inactivate, and (b) slowly activating "sleepy" channels that inactivate slowly if at all. Some fast channels are assumed to be converted to sleepy channels by cooling, possibly because of a phase transition in the membrane. The existence of sleepy channels complicates the determination of the Q10 of gating parameters and single-channel conductance. The Rockefeller University Press 1982-05-01 /pmc/articles/PMC2215509/ /pubmed/6284858 Text en 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 | Articles Evidence for a population of sleepy sodium channels in squid axon at low temperature |
title | Evidence for a population of sleepy sodium channels in squid axon at low temperature |
title_full | Evidence for a population of sleepy sodium channels in squid axon at low temperature |
title_fullStr | Evidence for a population of sleepy sodium channels in squid axon at low temperature |
title_full_unstemmed | Evidence for a population of sleepy sodium channels in squid axon at low temperature |
title_short | Evidence for a population of sleepy sodium channels in squid axon at low temperature |
title_sort | evidence for a population of sleepy sodium channels in squid axon at low temperature |
topic | Articles |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2215509/ https://www.ncbi.nlm.nih.gov/pubmed/6284858 |