| Influence of sodium ions on the membrane potential of the sino-atrial node in response to sympathetic nerve stimulation. | |
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MedLine Citation:
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PMID: 5664237 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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1. Sympathetic nerve-atrial preparations isolated from rabbits were used in the present study. Transmembrane potentials were recorded from sino-atrial (S-A) nodal pace-maker fibres.2. A reduction of [Na(+)](o) (extracellular concentration of sodium ions) decreased the maximal diastolic potential, reduced the size of the overshoot, prolonged the depolarization time, increased the rate of early repolarization and decreased the rate of late repolarization.3. A Na(+)-deficiency markedly augmented the positive chronotropic effect of stimulation of post-ganglionic sympathetic nerves at a frequency of 5/sec but slightly augmented the effect of stimulation at 1 and 20/sec.4. The marked membrane effect of sympathetic nerve stimulation at low [Na(+)](o) was an increase in the slope of slow depolarization during diastole. Corresponding to an induced acceleration of S-A nodal rate, the 90% duration of the action potential was decreased but the other action potential parameters measured were not influenced.5. A reduction of [Na(+)](o) to 51.7 mM produced in the pace-maker membrane, subthreshold oscillations the rate and the amplitude of which were increased by sympathetic nerve stimulation until conducted potentials were generated.6. It is presumed that cardiac noradrenaline elicits an increase in the slope of slow depolarization during late diastole which is due to an increase in Na(+) permeability, a decrease in K(+) permeability or a non-selective increase in ion permeability, but that it does not influence the pace-maker membrane during systole. |
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Authors:
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N Toda |
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Publication Detail:
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Type: In Vitro; Journal Article |
Journal Detail:
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Title: The Journal of physiology Volume: 196 ISSN: 0022-3751 ISO Abbreviation: J. Physiol. (Lond.) Publication Date: 1968 Jun |
Date Detail:
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Created Date: 1968-09-13 Completed Date: 1968-09-13 Revised Date: 2009-11-18 |
Medline Journal Info:
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Nlm Unique ID: 0266262 Medline TA: J Physiol Country: ENGLAND |
Other Details:
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Languages: eng Pagination: 677-91 Citation Subset: IM |
Export Citation:
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APA/MLA Format Download EndNote Download BibTex |
| MeSH Terms | |
Descriptor/Qualifier:
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Animals Cell Membrane Permeability Electric Stimulation Electrophysiology Female Heart Conduction System / drug effects* Male Membrane Potentials / drug effects* Norepinephrine / physiology Potassium / metabolism Rabbits Sinoatrial Node / drug effects Sodium / metabolism, pharmacology* Sympathetic Nervous System / physiology* Time Factors |
| Chemical | |
Reg. No./Substance:
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51-41-2/Norepinephrine; 7440-09-7/Potassium; 7440-23-5/Sodium |
| Comments/Corrections | |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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