Document Detail

Mechanisms underlying overdrive suppression and overdrive excitation in guinea pig sino-atrial node.
MedLine Citation:
PMID:  16715398     Owner:  NLM     Status:  MEDLINE    
The hypothesis that the pause that follows overdrive of the sino-atrial node (SAN) might be the net result of overdrive excitation and overdrive suppression was tested by studying rate and force patterns induced by overdrive in isolated guinea pig SAN superfused in vitro. In Tyrode solution, the pause is short and changes but little with longer or faster drives. In high [K(+)](o) solution, longer overdrives increase force percent-wise more than in Tyrode solution, shorten the pause and are followed by greater rate and force. When the SAN (quiescent in high [K(+)](o)) is driven at 6/min, faster overdrives are followed by stronger, slowly decreasing contractions. Alternating 10 s drives with 10 s pauses have little effect on force and rate in Tyrode solution, but progressively increase force and rate in high [K(+)](o). Cesium has effects similar to high [K(+)](o). High [Ca(2+)](o) increases force and in high [K(+)](o) increases the rate as well as it shortens the pause, whereas Ni(2+) decreases force as well as rate and lengthens the pause. Barium dissociates the effects on force and rate. Lidocaine and tetrodotoxin decrease rate and force, and increase the pause duration. In overdrive excitation, the increase in rate is associated with an enhancement of diastolic voltage oscillations. It is concluded that in SAN the prevalence of Ca(2+) load leads to overdrive excitation whereas the prevalence of Na(+) load leads to overdrive suppression. In Tyrode solution, the pause after drive appears to be the net result of these two different mechanisms.
Adam T Graziani; Mario Vassalle
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Publication Detail:
Type:  In Vitro; Journal Article; Research Support, N.I.H., Extramural; Research Support, Non-U.S. Gov't     Date:  2006-05-21
Journal Detail:
Title:  Journal of biomedical science     Volume:  13     ISSN:  1021-7770     ISO Abbreviation:  J. Biomed. Sci.     Publication Date:  2006 Sep 
Date Detail:
Created Date:  2006-09-29     Completed Date:  2007-01-24     Revised Date:  2007-12-03    
Medline Journal Info:
Nlm Unique ID:  9421567     Medline TA:  J Biomed Sci     Country:  Netherlands    
Other Details:
Languages:  eng     Pagination:  703-20     Citation Subset:  IM    
Department of Physiology and Pharmacology, State University of New York, Downstate Medical Center, 450 Clarkson Avenue, Box 31, Brooklyn, NY 11203, USA.
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MeSH Terms
Barium / pharmacology
Calcium / metabolism*
Cesium / pharmacology
Guinea Pigs
Isotonic Solutions / pharmacology
Nickel / pharmacology
Potassium / pharmacology
Sinoatrial Node / drug effects,  metabolism*
Sodium / metabolism*
Sodium Channel Blockers / pharmacology
Grant Support
Reg. No./Substance:
0/Isotonic Solutions; 0/Sodium Channel Blockers; 0/Tyrode's solution; 7440-02-0/Nickel; 7440-09-7/Potassium; 7440-23-5/Sodium; 7440-39-3/Barium; 7440-46-2/Cesium; 7440-70-2/Calcium

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

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