The early phase of sodium channel gating current in the squid giant axon. Characteristics of a fast component of displacement charge movement
A fast component of displacement current which accompanies the sodium channel gating current has been recorded from the membrane of the giant axon of the squid Loligo forbesii. This component is characterized by relaxation time constants typically shorter than 25 microseconds. The charge displaced a...
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Veröffentlicht in: | European biophysics journal 1992-05, Vol.21 (2), p.99-116 |
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description | A fast component of displacement current which accompanies the sodium channel gating current has been recorded from the membrane of the giant axon of the squid Loligo forbesii. This component is characterized by relaxation time constants typically shorter than 25 microseconds. The charge displaced accounts for about 10% (or 2 nC/cm2) of the total displacement charge attributed to voltage-dependent sodium channels. Using a low noise, wide-band voltage clamp system and specially designed voltage step protocols we could demonstrate that this component: (i) is not a recording artifact; (ii) is kinetically independent from the sodium channel activation and inactivation processes; (iii) can account for a significant fraction of the initial amplitude of recorded displacement current and (iv) has a steady state charge transfer which saturates for membrane potentials above +20 mV and below -100 mV. This component can be modelled as a single step transition using the Eyring-Boltzmann formalism with a quantal charge of 1 e- and an asymmetrical energy barrier. Furthermore, if it were associated with the squid sodium channel, our data would suggest one fast transition per channel. A possible role as a sodium channel activation trigger, which would still be consistent with kinetic independence, is discussed. Despite uncertainties about its origin, the property of kinetic independence allows subtraction of this component from the total displacement current to reveal a rising phase in the early time course of the remaining current. This will have to be taken into account when modelling the voltage-dependent sodium channel. |
doi_str_mv | 10.1007/BF00185425 |
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Characteristics of a fast component of displacement charge movement</title><source>MEDLINE</source><source>SpringerNature Journals</source><creator>FORSTER, I. C ; GREEFF, N. G</creator><creatorcontrib>FORSTER, I. C ; GREEFF, N. G</creatorcontrib><description>A fast component of displacement current which accompanies the sodium channel gating current has been recorded from the membrane of the giant axon of the squid Loligo forbesii. This component is characterized by relaxation time constants typically shorter than 25 microseconds. The charge displaced accounts for about 10% (or 2 nC/cm2) of the total displacement charge attributed to voltage-dependent sodium channels. Using a low noise, wide-band voltage clamp system and specially designed voltage step protocols we could demonstrate that this component: (i) is not a recording artifact; (ii) is kinetically independent from the sodium channel activation and inactivation processes; (iii) can account for a significant fraction of the initial amplitude of recorded displacement current and (iv) has a steady state charge transfer which saturates for membrane potentials above +20 mV and below -100 mV. This component can be modelled as a single step transition using the Eyring-Boltzmann formalism with a quantal charge of 1 e- and an asymmetrical energy barrier. Furthermore, if it were associated with the squid sodium channel, our data would suggest one fast transition per channel. A possible role as a sodium channel activation trigger, which would still be consistent with kinetic independence, is discussed. Despite uncertainties about its origin, the property of kinetic independence allows subtraction of this component from the total displacement current to reveal a rising phase in the early time course of the remaining current. This will have to be taken into account when modelling the voltage-dependent sodium channel.</description><identifier>ISSN: 0175-7571</identifier><identifier>EISSN: 1432-1017</identifier><identifier>DOI: 10.1007/BF00185425</identifier><identifier>PMID: 1327730</identifier><language>eng</language><publisher>Berlin: Springer</publisher><subject>Animals ; Axons - metabolism ; Biological and medical sciences ; Biophysical Phenomena ; Biophysics ; Cell physiology ; Decapodiformes ; Electrochemistry ; Fundamental and applied biological sciences. Psychology ; In Vitro Techniques ; Ion Channel Gating - physiology ; Kinetics ; Membrane and intracellular transports ; Membrane Potentials ; Models, Biological ; Molecular and cellular biology ; Sodium Channels - metabolism</subject><ispartof>European biophysics journal, 1992-05, Vol.21 (2), p.99-116</ispartof><rights>1992 INIST-CNRS</rights><lds50>peer_reviewed</lds50><woscitedreferencessubscribed>false</woscitedreferencessubscribed></display><links><openurl>$$Topenurl_article</openurl><openurlfulltext>$$Topenurlfull_article</openurlfulltext><thumbnail>$$Tsyndetics_thumb_exl</thumbnail><link.rule.ids>314,780,784,27924,27925</link.rule.ids><backlink>$$Uhttp://pascal-francis.inist.fr/vibad/index.php?action=getRecordDetail&idt=5433347$$DView record in Pascal Francis$$Hfree_for_read</backlink><backlink>$$Uhttps://www.ncbi.nlm.nih.gov/pubmed/1327730$$D View this record in MEDLINE/PubMed$$Hfree_for_read</backlink></links><search><creatorcontrib>FORSTER, I. C</creatorcontrib><creatorcontrib>GREEFF, N. G</creatorcontrib><title>The early phase of sodium channel gating current in the squid giant axon. Characteristics of a fast component of displacement charge movement</title><title>European biophysics journal</title><addtitle>Eur Biophys J</addtitle><description>A fast component of displacement current which accompanies the sodium channel gating current has been recorded from the membrane of the giant axon of the squid Loligo forbesii. This component is characterized by relaxation time constants typically shorter than 25 microseconds. The charge displaced accounts for about 10% (or 2 nC/cm2) of the total displacement charge attributed to voltage-dependent sodium channels. Using a low noise, wide-band voltage clamp system and specially designed voltage step protocols we could demonstrate that this component: (i) is not a recording artifact; (ii) is kinetically independent from the sodium channel activation and inactivation processes; (iii) can account for a significant fraction of the initial amplitude of recorded displacement current and (iv) has a steady state charge transfer which saturates for membrane potentials above +20 mV and below -100 mV. This component can be modelled as a single step transition using the Eyring-Boltzmann formalism with a quantal charge of 1 e- and an asymmetrical energy barrier. Furthermore, if it were associated with the squid sodium channel, our data would suggest one fast transition per channel. A possible role as a sodium channel activation trigger, which would still be consistent with kinetic independence, is discussed. Despite uncertainties about its origin, the property of kinetic independence allows subtraction of this component from the total displacement current to reveal a rising phase in the early time course of the remaining current. This will have to be taken into account when modelling the voltage-dependent sodium channel.</description><subject>Animals</subject><subject>Axons - metabolism</subject><subject>Biological and medical sciences</subject><subject>Biophysical Phenomena</subject><subject>Biophysics</subject><subject>Cell physiology</subject><subject>Decapodiformes</subject><subject>Electrochemistry</subject><subject>Fundamental and applied biological sciences. Psychology</subject><subject>In Vitro Techniques</subject><subject>Ion Channel Gating - physiology</subject><subject>Kinetics</subject><subject>Membrane and intracellular transports</subject><subject>Membrane Potentials</subject><subject>Models, Biological</subject><subject>Molecular and cellular biology</subject><subject>Sodium Channels - metabolism</subject><issn>0175-7571</issn><issn>1432-1017</issn><fulltext>true</fulltext><rsrctype>article</rsrctype><creationdate>1992</creationdate><recordtype>article</recordtype><sourceid>EIF</sourceid><recordid>eNpFkE9r3DAQxUVJSbZpL70HdAg9FJzqj7VyjsnStIVAL-nZjKXxroItORo7NB-i37na7tJcZph5v3kDj7GPUlxJIeyX2zshZGNqZd6wlay1qqSQ9oStSjWVNVaesXdEj0LURsrmlJ1KrazVYsX-POyQI-ThhU87IOSp55R8WEbudhAjDnwLc4hb7pacMc48RD6XG3pagufbAGUFv1O84psdZHAz5kBzcLR3At4DzdylcUpxf1x2PtA0gMNxP5cfeYt8TM__5vfsbQ8D4YdjP2e_7r4-bL5X9z-__djc3FdOWTFXxngvAbzRINbaY2MaZ8xais5ZDfJ67VUJobHYFRFFJxUaJTsBKHxn1r0-Z58OvlNOTwvS3I6BHA4DREwLtVYrpa5NU8DPB9DlRJSxb6ccRsgvrRTtPvv2NfsCXxxdl25E_4oewi765VEHcjD0GaIL9B8ztda6tvovR3yNEg</recordid><startdate>19920501</startdate><enddate>19920501</enddate><creator>FORSTER, I. 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G</author></sort><facets><frbrtype>5</frbrtype><frbrgroupid>cdi_FETCH-LOGICAL-c270t-55dd1aad53a063de858c55610bc73a196d243287eb3dee0b12e521b0ae0db56f3</frbrgroupid><rsrctype>articles</rsrctype><prefilter>articles</prefilter><language>eng</language><creationdate>1992</creationdate><topic>Animals</topic><topic>Axons - metabolism</topic><topic>Biological and medical sciences</topic><topic>Biophysical Phenomena</topic><topic>Biophysics</topic><topic>Cell physiology</topic><topic>Decapodiformes</topic><topic>Electrochemistry</topic><topic>Fundamental and applied biological sciences. Psychology</topic><topic>In Vitro Techniques</topic><topic>Ion Channel Gating - physiology</topic><topic>Kinetics</topic><topic>Membrane and intracellular transports</topic><topic>Membrane Potentials</topic><topic>Models, Biological</topic><topic>Molecular and cellular biology</topic><topic>Sodium Channels - metabolism</topic><toplevel>peer_reviewed</toplevel><toplevel>online_resources</toplevel><creatorcontrib>FORSTER, I. C</creatorcontrib><creatorcontrib>GREEFF, N. G</creatorcontrib><collection>Pascal-Francis</collection><collection>Medline</collection><collection>MEDLINE</collection><collection>MEDLINE (Ovid)</collection><collection>MEDLINE</collection><collection>MEDLINE</collection><collection>PubMed</collection><collection>CrossRef</collection><collection>MEDLINE - Academic</collection><jtitle>European biophysics journal</jtitle></facets><delivery><delcategory>Remote Search Resource</delcategory><fulltext>fulltext</fulltext></delivery><addata><au>FORSTER, I. C</au><au>GREEFF, N. G</au><format>journal</format><genre>article</genre><ristype>JOUR</ristype><atitle>The early phase of sodium channel gating current in the squid giant axon. Characteristics of a fast component of displacement charge movement</atitle><jtitle>European biophysics journal</jtitle><addtitle>Eur Biophys J</addtitle><date>1992-05-01</date><risdate>1992</risdate><volume>21</volume><issue>2</issue><spage>99</spage><epage>116</epage><pages>99-116</pages><issn>0175-7571</issn><eissn>1432-1017</eissn><abstract>A fast component of displacement current which accompanies the sodium channel gating current has been recorded from the membrane of the giant axon of the squid Loligo forbesii. This component is characterized by relaxation time constants typically shorter than 25 microseconds. The charge displaced accounts for about 10% (or 2 nC/cm2) of the total displacement charge attributed to voltage-dependent sodium channels. Using a low noise, wide-band voltage clamp system and specially designed voltage step protocols we could demonstrate that this component: (i) is not a recording artifact; (ii) is kinetically independent from the sodium channel activation and inactivation processes; (iii) can account for a significant fraction of the initial amplitude of recorded displacement current and (iv) has a steady state charge transfer which saturates for membrane potentials above +20 mV and below -100 mV. This component can be modelled as a single step transition using the Eyring-Boltzmann formalism with a quantal charge of 1 e- and an asymmetrical energy barrier. Furthermore, if it were associated with the squid sodium channel, our data would suggest one fast transition per channel. A possible role as a sodium channel activation trigger, which would still be consistent with kinetic independence, is discussed. Despite uncertainties about its origin, the property of kinetic independence allows subtraction of this component from the total displacement current to reveal a rising phase in the early time course of the remaining current. This will have to be taken into account when modelling the voltage-dependent sodium channel.</abstract><cop>Berlin</cop><pub>Springer</pub><pmid>1327730</pmid><doi>10.1007/BF00185425</doi><tpages>18</tpages></addata></record> |
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subjects | Animals Axons - metabolism Biological and medical sciences Biophysical Phenomena Biophysics Cell physiology Decapodiformes Electrochemistry Fundamental and applied biological sciences. Psychology In Vitro Techniques Ion Channel Gating - physiology Kinetics Membrane and intracellular transports Membrane Potentials Models, Biological Molecular and cellular biology Sodium Channels - metabolism |
title | The early phase of sodium channel gating current in the squid giant axon. Characteristics of a fast component of displacement charge movement |
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