Document Detail

Influence of sodium ions on the membrane potential of the sino-atrial node in response to sympathetic nerve stimulation.
MedLine Citation:
PMID:  5664237     Owner:  NLM     Status:  MEDLINE    
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.
N Toda
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Publication Detail:
Type:  In Vitro; Journal Article    
Journal Detail:
Title:  The Journal of physiology     Volume:  196     ISSN:  0022-3751     ISO Abbreviation:  J. Physiol. (Lond.)     Publication Date:  1968 Jun 
Date Detail:
Created Date:  1968-09-13     Completed Date:  1968-09-13     Revised Date:  2009-11-18    
Medline Journal Info:
Nlm Unique ID:  0266262     Medline TA:  J Physiol     Country:  ENGLAND    
Other Details:
Languages:  eng     Pagination:  677-91     Citation Subset:  IM    
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MeSH Terms
Cell Membrane Permeability
Electric Stimulation
Heart Conduction System / drug effects*
Membrane Potentials / drug effects*
Norepinephrine / physiology
Potassium / metabolism
Sinoatrial Node / drug effects
Sodium / metabolism,  pharmacology*
Sympathetic Nervous System / physiology*
Time Factors
Reg. No./Substance:
51-41-2/Norepinephrine; 7440-09-7/Potassium; 7440-23-5/Sodium

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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