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rdf:type |
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lifeskim:mentions |
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pubmed:dateCreated |
1995-1-26
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pubmed:abstractText |
1. A potassium channel activated by internal Na+ ions (K+Na channel) was identified in peripheral myelinated axons of Xenopus laevis using the cell-attached and excised configurations of the patch clamp technique. 2. The single-channel conductance for the main open state was 88 pS with [K+]o = 105 mM and pS with [K+]o = 2.5 mM ([K+]i = 105 mM). The channel was selectively permeable to K+ over Na+ ions. A characteristic feature of the K+Na channel was the frequent occurrence of subconductance states. 3. The open probability of the channel was strongly dependent on the concentration of Na+ ions at the inner side of the membrane. The half-maximal activating Na+ concentration and the Hill coefficient were 33 mM and 2.9, respectively. The open probability of the channel showed only weak potential dependence. 4. The K+Na channel was relatively insensitive to external tetraethylammonium (TEA+) in comparison with voltage-dependent axonal K+ channels; the half-maximal inhibitory concentration (IC50) was 21.3 mM (at -90 mV). In contrast, the channel was blocked by low concentrations of external Ba2+ and Cs+ ions, with IC50 values of 0.7 and 1.1 mM, respectively (at -90 mV). The block by Ba2+ and Cs+ was more pronounced at negative than at positive membrane potentials. 5. A comparison of the number of K+Na channels in nodal and paranodal patches from the same axon revealed that the channel density was about 10-fold higher at the node of Ranvier than at the paranode. Moreover, a correlation between the number of K+Na channels and voltage-dependent Na+ channels in the same patches was found, suggesting co-localization of both channel types. 6. As weakly potential-dependent ('leakage') channels, axonal K+Na channels may be involved in setting the resting potential of vertebrate axons. Simulations of Na+ ion diffusion suggest two possible mechanisms of activation of K+Na channels: the local increase of Na+ concentration in a cluster of Na+ channels during a single action potential or the accumulation in the intracellular axonal compartment during a train of action potentials.
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pubmed:commentsCorrections |
http://linkedlifedata.com/resource/pubmed/commentcorrection/7799220-10735,
http://linkedlifedata.com/resource/pubmed/commentcorrection/7799220-1080274,
http://linkedlifedata.com/resource/pubmed/commentcorrection/7799220-1291683,
http://linkedlifedata.com/resource/pubmed/commentcorrection/7799220-14191481,
http://linkedlifedata.com/resource/pubmed/commentcorrection/7799220-1508412,
http://linkedlifedata.com/resource/pubmed/commentcorrection/7799220-1578280,
http://linkedlifedata.com/resource/pubmed/commentcorrection/7799220-1770447,
http://linkedlifedata.com/resource/pubmed/commentcorrection/7799220-1841940,
http://linkedlifedata.com/resource/pubmed/commentcorrection/7799220-2041727,
http://linkedlifedata.com/resource/pubmed/commentcorrection/7799220-2163435,
http://linkedlifedata.com/resource/pubmed/commentcorrection/7799220-2413369,
http://linkedlifedata.com/resource/pubmed/commentcorrection/7799220-2550937,
http://linkedlifedata.com/resource/pubmed/commentcorrection/7799220-2795480,
http://linkedlifedata.com/resource/pubmed/commentcorrection/7799220-2849627,
http://linkedlifedata.com/resource/pubmed/commentcorrection/7799220-318061,
http://linkedlifedata.com/resource/pubmed/commentcorrection/7799220-4188682,
http://linkedlifedata.com/resource/pubmed/commentcorrection/7799220-4555514,
http://linkedlifedata.com/resource/pubmed/commentcorrection/7799220-5350329,
http://linkedlifedata.com/resource/pubmed/commentcorrection/7799220-5463657,
http://linkedlifedata.com/resource/pubmed/commentcorrection/7799220-5846933,
http://linkedlifedata.com/resource/pubmed/commentcorrection/7799220-6033586,
http://linkedlifedata.com/resource/pubmed/commentcorrection/7799220-6270629,
http://linkedlifedata.com/resource/pubmed/commentcorrection/7799220-6278324,
http://linkedlifedata.com/resource/pubmed/commentcorrection/7799220-6328309,
http://linkedlifedata.com/resource/pubmed/commentcorrection/7799220-6601260,
http://linkedlifedata.com/resource/pubmed/commentcorrection/7799220-6728648,
http://linkedlifedata.com/resource/pubmed/commentcorrection/7799220-6884495,
http://linkedlifedata.com/resource/pubmed/commentcorrection/7799220-7045870,
http://linkedlifedata.com/resource/pubmed/commentcorrection/7799220-8387591,
http://linkedlifedata.com/resource/pubmed/commentcorrection/7799220-8392569,
http://linkedlifedata.com/resource/pubmed/commentcorrection/7799220-8474685
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pubmed:language |
eng
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pubmed:journal |
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pubmed:citationSubset |
IM
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pubmed:chemical |
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pubmed:status |
MEDLINE
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pubmed:month |
Sep
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pubmed:issn |
0022-3751
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pubmed:author |
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pubmed:issnType |
Print
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pubmed:day |
1
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pubmed:volume |
479 ( Pt 2)
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pubmed:owner |
NLM
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pubmed:authorsComplete |
Y
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pubmed:pagination |
183-97
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pubmed:dateRevised |
2009-11-18
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pubmed:meshHeading |
pubmed-meshheading:7799220-Animals,
pubmed-meshheading:7799220-Axons,
pubmed-meshheading:7799220-Barium,
pubmed-meshheading:7799220-Cell Membrane Permeability,
pubmed-meshheading:7799220-Cesium,
pubmed-meshheading:7799220-Demyelinating Diseases,
pubmed-meshheading:7799220-Immunohistochemistry,
pubmed-meshheading:7799220-Membrane Potentials,
pubmed-meshheading:7799220-Microscopy, Electron,
pubmed-meshheading:7799220-Myelin Sheath,
pubmed-meshheading:7799220-Patch-Clamp Techniques,
pubmed-meshheading:7799220-Potassium Channel Blockers,
pubmed-meshheading:7799220-Potassium Channels,
pubmed-meshheading:7799220-Ranvier's Nodes,
pubmed-meshheading:7799220-Sodium,
pubmed-meshheading:7799220-Sodium Channels,
pubmed-meshheading:7799220-Tetraethylammonium,
pubmed-meshheading:7799220-Tetraethylammonium Compounds,
pubmed-meshheading:7799220-Xenopus laevis
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pubmed:year |
1994
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pubmed:articleTitle |
Na(+)-activated K+ channels localized in the nodal region of myelinated axons of Xenopus.
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pubmed:affiliation |
Physiologisches Institut, Justus-Liebig-Universität, Giessen, Germany.
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pubmed:publicationType |
Journal Article,
Comparative Study,
Research Support, Non-U.S. Gov't
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