Document Detail

Regional differences in rabbit atrial repolarization: importance of transient outward current.
MedLine Citation:
PMID:  8141365     Owner:  NLM     Status:  MEDLINE    
Regional differences in rabbit atrial repolarization were investigated using a conventional microelectrode technique. A more rapid phase 1 repolarization (lower phase 1 amplitude) was seen in the left atrial (LA) roof area compared with the right atrial (RA) roof area: 54 +/- 10 vs. 82 +/- 6 mV at 1,000 ms (P < 0.001). In addition, action potential duration at 40 mV above the resting potential (APD40) was shorter in LA and was associated with a slower phase 3 repolarization rate. Furthermore, the recovery time constant of phase 1 amplitude at 500 ms was 0.9 +/- 0.2 s in LA and 3.5 +/- 1.5 s in RA (P < 0.001). Pacing cycle lengths (2,000, 1,500, 1,000, 800, and 500 ms) modulated phase 1 amplitude, APD40, and phase 3 rate in both regions. 4-Aminopyridine (4-AP; 1 mM), a selective transient outward current (I(to)) blocker, abolished cycle length dependence of the above action potential parameters and diminished the differences in electrophysiological properties between the two regions. 4-AP also flattened the restitution curve of phase 1 amplitude in both regions. In conclusion, the findings suggest that the different kinetics of I(to) play an important role in regional differences of atrial repolarization.
A Qi; J A Yeung-Lai-Wah; J Xiao; C R Kerr
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  The American journal of physiology     Volume:  266     ISSN:  0002-9513     ISO Abbreviation:  Am. J. Physiol.     Publication Date:  1994 Feb 
Date Detail:
Created Date:  1994-04-26     Completed Date:  1994-04-26     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  0370511     Medline TA:  Am J Physiol     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  H643-9     Citation Subset:  IM    
Department of Medicine, University of British Columbia, Vancouver, Canada.
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MeSH Terms
4-Aminopyridine / pharmacology
Action Potentials / drug effects,  physiology*
Analysis of Variance
Electric Stimulation
Heart / drug effects,  physiology*
Heart Atria
Membrane Potentials
Time Factors
Reg. No./Substance:

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