Outwardly rectifying deflections in threshold electrotonus due to K+ conductances
A transient decrease in excitability occurs regularly during the S1 phase of threshold electrotonus to depolarizing conditioning stimuli for sensory and, less frequently, motor axons. This has been attributed to the outwardly rectifying action of fast K + channels, at least in patients with demyelin...
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description | A transient decrease in excitability occurs regularly during the S1 phase of threshold electrotonus to depolarizing conditioning
stimuli for sensory and, less frequently, motor axons. This has been attributed to the outwardly rectifying action of fast
K + channels, at least in patients with demyelinating diseases. This study investigates the genesis of this notch in healthy axons. Threshold electrotonus was recorded for sensory and motor axons in the median nerve at the wrist in response
to test stimuli of different width. The notch occurred more frequently the briefer the test stimulus, and more frequently
in sensory studies. In studies on motor axons, the notch decreased in latency and increased in amplitude as the conditioning
stimulus increased or the limb was cooled. Low-threshold axons displayed profound changes in strengthâduration time constant
even though the threshold electrotonus curves contained no detectable notch. When a 1.0 ms current was added to subthreshold
conditioning stimuli to trigger EMG, the notch varied with the timing and intensity of the brief current pulse. This study
finds no evidence for an outwardly rectifying deflection due to K + channels, other than the slow accommodation attributable to slow K + currents. In normal motor axons, a depolarization-induced notch during the S1 phase of threshold electrotonus is the result
of the conditioning stimulus exceeding threshold for some axons. The notch is more apparent in sensory axons probably because
of the lower slope of the stimulusâresponse curve and their longer strengthâduration time constant rather than a difference
in K + conductances. This may also explain the notch in demyelinating diseases. |
doi_str_mv | 10.1113/jphysiol.2006.126003 |
format | Article |
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stimuli for sensory and, less frequently, motor axons. This has been attributed to the outwardly rectifying action of fast
K + channels, at least in patients with demyelinating diseases. This study investigates the genesis of this notch in healthy axons. Threshold electrotonus was recorded for sensory and motor axons in the median nerve at the wrist in response
to test stimuli of different width. The notch occurred more frequently the briefer the test stimulus, and more frequently
in sensory studies. In studies on motor axons, the notch decreased in latency and increased in amplitude as the conditioning
stimulus increased or the limb was cooled. Low-threshold axons displayed profound changes in strengthâduration time constant
even though the threshold electrotonus curves contained no detectable notch. When a 1.0 ms current was added to subthreshold
conditioning stimuli to trigger EMG, the notch varied with the timing and intensity of the brief current pulse. This study
finds no evidence for an outwardly rectifying deflection due to K + channels, other than the slow accommodation attributable to slow K + currents. In normal motor axons, a depolarization-induced notch during the S1 phase of threshold electrotonus is the result
of the conditioning stimulus exceeding threshold for some axons. The notch is more apparent in sensory axons probably because
of the lower slope of the stimulusâresponse curve and their longer strengthâduration time constant rather than a difference
in K + conductances. This may also explain the notch in demyelinating diseases.</description><identifier>ISSN: 0022-3751</identifier><identifier>EISSN: 1469-7793</identifier><identifier>DOI: 10.1113/jphysiol.2006.126003</identifier><identifier>PMID: 17272346</identifier><language>eng</language><publisher>Oxford, UK: The Physiological Society</publisher><subject>Adult ; Axons - physiology ; Electromyography ; Electrophysiology ; Female ; Humans ; Integrative ; Male ; Middle Aged ; Motor Neurons - physiology ; Potassium - metabolism ; Potassium Channels - physiology</subject><ispartof>The Journal of physiology, 2007-04, Vol.580 (2), p.685-696</ispartof><rights>2007 The Journal of Physiology © 2007 The Physiological Society</rights><rights>2007 The Authors. Journal compilation © 2007 The Physiological Society 2007</rights><lds50>peer_reviewed</lds50><oa>free_for_read</oa><woscitedreferencessubscribed>false</woscitedreferencessubscribed><citedby>FETCH-LOGICAL-c5236-7977e00a052d9ddf961e6b79f3b63b6edd0b42f2e7cda717d8aab379351660b03</citedby><cites>FETCH-LOGICAL-c5236-7977e00a052d9ddf961e6b79f3b63b6edd0b42f2e7cda717d8aab379351660b03</cites></display><links><openurl>$$Topenurl_article</openurl><openurlfulltext>$$Topenurlfull_article</openurlfulltext><thumbnail>$$Tsyndetics_thumb_exl</thumbnail><linktopdf>$$Uhttps://www.ncbi.nlm.nih.gov/pmc/articles/PMC2075549/pdf/$$EPDF$$P50$$Gpubmedcentral$$H</linktopdf><linktohtml>$$Uhttps://www.ncbi.nlm.nih.gov/pmc/articles/PMC2075549/$$EHTML$$P50$$Gpubmedcentral$$H</linktohtml><link.rule.ids>230,314,727,780,784,885,1417,1433,27924,27925,45574,45575,46409,46833,53791,53793</link.rule.ids><backlink>$$Uhttps://www.ncbi.nlm.nih.gov/pubmed/17272346$$D View this record in MEDLINE/PubMed$$Hfree_for_read</backlink></links><search><creatorcontrib>Trevillion, Louise</creatorcontrib><creatorcontrib>Howells, James</creatorcontrib><creatorcontrib>Burke, David</creatorcontrib><title>Outwardly rectifying deflections in threshold electrotonus due to K+ conductances</title><title>The Journal of physiology</title><addtitle>J Physiol</addtitle><description>A transient decrease in excitability occurs regularly during the S1 phase of threshold electrotonus to depolarizing conditioning
stimuli for sensory and, less frequently, motor axons. This has been attributed to the outwardly rectifying action of fast
K + channels, at least in patients with demyelinating diseases. This study investigates the genesis of this notch in healthy axons. Threshold electrotonus was recorded for sensory and motor axons in the median nerve at the wrist in response
to test stimuli of different width. The notch occurred more frequently the briefer the test stimulus, and more frequently
in sensory studies. In studies on motor axons, the notch decreased in latency and increased in amplitude as the conditioning
stimulus increased or the limb was cooled. Low-threshold axons displayed profound changes in strengthâduration time constant
even though the threshold electrotonus curves contained no detectable notch. When a 1.0 ms current was added to subthreshold
conditioning stimuli to trigger EMG, the notch varied with the timing and intensity of the brief current pulse. This study
finds no evidence for an outwardly rectifying deflection due to K + channels, other than the slow accommodation attributable to slow K + currents. In normal motor axons, a depolarization-induced notch during the S1 phase of threshold electrotonus is the result
of the conditioning stimulus exceeding threshold for some axons. The notch is more apparent in sensory axons probably because
of the lower slope of the stimulusâresponse curve and their longer strengthâduration time constant rather than a difference
in K + conductances. This may also explain the notch in demyelinating diseases.</description><subject>Adult</subject><subject>Axons - physiology</subject><subject>Electromyography</subject><subject>Electrophysiology</subject><subject>Female</subject><subject>Humans</subject><subject>Integrative</subject><subject>Male</subject><subject>Middle Aged</subject><subject>Motor Neurons - physiology</subject><subject>Potassium - metabolism</subject><subject>Potassium Channels - physiology</subject><issn>0022-3751</issn><issn>1469-7793</issn><fulltext>true</fulltext><rsrctype>article</rsrctype><creationdate>2007</creationdate><recordtype>article</recordtype><sourceid>EIF</sourceid><recordid>eNqNkM1q3DAUhUVpaSZJ36AU7boonl5JtjTaFEpo059AGkjXQpauxwqONUh2B799bJz-7QICIel856KPkNcMtowx8f7u0E45xG7LAeSWcQkgnpENK6UulNLiOdkAcF4IVbETcprzHQAToPVLcsIUV1yUckNursfhaJPvJprQDaGZQr-nHptuOcU-09DToU2Y29h5ist1ikPsx0z9iHSI9Ps76mLvRzfY3mE-Jy8a22V89bifkZ-fP91efCmuri-_Xny8KlzFhSyUVgoBLFTca-8bLRnKWulG1HJe6D3UJW84KuetYsrvrK3F_K-KSQk1iDPyYe09jPU9eof9kGxnDinc2zSZaIP5_6UPrdnHX4aDqqpSzwXlWuBSzDlh84dlYBbF5rdisyg2q-IZe_Pv3L_Qo9M5oNfAMXQ4PanU3H77wWG3sG9Xtg379hgSmjWdows4TKbageFG7irxAPzgnPI</recordid><startdate>20070415</startdate><enddate>20070415</enddate><creator>Trevillion, Louise</creator><creator>Howells, James</creator><creator>Burke, David</creator><general>The Physiological Society</general><general>Blackwell Publishing Ltd</general><general>Blackwell Science Inc</general><scope>CGR</scope><scope>CUY</scope><scope>CVF</scope><scope>ECM</scope><scope>EIF</scope><scope>NPM</scope><scope>AAYXX</scope><scope>CITATION</scope><scope>5PM</scope></search><sort><creationdate>20070415</creationdate><title>Outwardly rectifying deflections in threshold electrotonus due to K+ conductances</title><author>Trevillion, Louise ; Howells, James ; Burke, David</author></sort><facets><frbrtype>5</frbrtype><frbrgroupid>cdi_FETCH-LOGICAL-c5236-7977e00a052d9ddf961e6b79f3b63b6edd0b42f2e7cda717d8aab379351660b03</frbrgroupid><rsrctype>articles</rsrctype><prefilter>articles</prefilter><language>eng</language><creationdate>2007</creationdate><topic>Adult</topic><topic>Axons - physiology</topic><topic>Electromyography</topic><topic>Electrophysiology</topic><topic>Female</topic><topic>Humans</topic><topic>Integrative</topic><topic>Male</topic><topic>Middle Aged</topic><topic>Motor Neurons - physiology</topic><topic>Potassium - metabolism</topic><topic>Potassium Channels - physiology</topic><toplevel>peer_reviewed</toplevel><toplevel>online_resources</toplevel><creatorcontrib>Trevillion, Louise</creatorcontrib><creatorcontrib>Howells, James</creatorcontrib><creatorcontrib>Burke, David</creatorcontrib><collection>Medline</collection><collection>MEDLINE</collection><collection>MEDLINE (Ovid)</collection><collection>MEDLINE</collection><collection>MEDLINE</collection><collection>PubMed</collection><collection>CrossRef</collection><collection>PubMed Central (Full Participant titles)</collection><jtitle>The Journal of physiology</jtitle></facets><delivery><delcategory>Remote Search Resource</delcategory><fulltext>fulltext</fulltext></delivery><addata><au>Trevillion, Louise</au><au>Howells, James</au><au>Burke, David</au><format>journal</format><genre>article</genre><ristype>JOUR</ristype><atitle>Outwardly rectifying deflections in threshold electrotonus due to K+ conductances</atitle><jtitle>The Journal of physiology</jtitle><addtitle>J Physiol</addtitle><date>2007-04-15</date><risdate>2007</risdate><volume>580</volume><issue>2</issue><spage>685</spage><epage>696</epage><pages>685-696</pages><issn>0022-3751</issn><eissn>1469-7793</eissn><abstract>A transient decrease in excitability occurs regularly during the S1 phase of threshold electrotonus to depolarizing conditioning
stimuli for sensory and, less frequently, motor axons. This has been attributed to the outwardly rectifying action of fast
K + channels, at least in patients with demyelinating diseases. This study investigates the genesis of this notch in healthy axons. Threshold electrotonus was recorded for sensory and motor axons in the median nerve at the wrist in response
to test stimuli of different width. The notch occurred more frequently the briefer the test stimulus, and more frequently
in sensory studies. In studies on motor axons, the notch decreased in latency and increased in amplitude as the conditioning
stimulus increased or the limb was cooled. Low-threshold axons displayed profound changes in strengthâduration time constant
even though the threshold electrotonus curves contained no detectable notch. When a 1.0 ms current was added to subthreshold
conditioning stimuli to trigger EMG, the notch varied with the timing and intensity of the brief current pulse. This study
finds no evidence for an outwardly rectifying deflection due to K + channels, other than the slow accommodation attributable to slow K + currents. In normal motor axons, a depolarization-induced notch during the S1 phase of threshold electrotonus is the result
of the conditioning stimulus exceeding threshold for some axons. The notch is more apparent in sensory axons probably because
of the lower slope of the stimulusâresponse curve and their longer strengthâduration time constant rather than a difference
in K + conductances. This may also explain the notch in demyelinating diseases.</abstract><cop>Oxford, UK</cop><pub>The Physiological Society</pub><pmid>17272346</pmid><doi>10.1113/jphysiol.2006.126003</doi><tpages>12</tpages><oa>free_for_read</oa></addata></record> |
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source | MEDLINE; Access via Wiley Online Library; IngentaConnect Free/Open Access Journals; EZB-FREE-00999 freely available EZB journals; Wiley Online Library (Open Access Collection); PubMed Central |
subjects | Adult Axons - physiology Electromyography Electrophysiology Female Humans Integrative Male Middle Aged Motor Neurons - physiology Potassium - metabolism Potassium Channels - physiology |
title | Outwardly rectifying deflections in threshold electrotonus due to K+ conductances |
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