title: Characterization of conduction in the ventricles of normal and heterozygous Cx43 knockout mice using optical mapping.
abstract: BACKGROUND
  Gap junction channels are important determinants of conduction in the heart and may play a central role in the development of lethal cardiac arrhythmias. The recent development of a Cx43-deficient mouse has raised fundamental questions about the role of specific connexin isoforms in intercellular communication in the heart. Although a homozygous null mutation of the Cx43 gene (Cx43-/-) is lethal, the heterozygous (Cx43+/-) animals survive to adulthood. Reports on the cardiac electrophysiologic phenotype of the Cx43+/- mice are contradictory. Thus, the effects of a null mutation of a single Cx43 allele require reevaluation.
  
  
  RESULTS
  High-resolution video mapping techniques were used to study propagation in hearts from Cx43+/- and littermate control (Cx43+/+) mice. Local conduction velocities (CVs) and conduction patterns were quantitatively measured by determining conduction vectors. We undertook the characterization of ECG parameters and epicardial CVs of normal and Cx43+/- mouse hearts. ECG measurements obtained from 12 Cx43+/+ and 6 Cx43+/- age matched mice did not show differences in any parameter, including QRS duration (14.5 +/- 0.9 and 15.7 +/- 2.3 msec for Cx43+/+ and Cx43+/-, respectively). In addition, using a sensitive method of detecting changes in local CV, video images of epicardial wave propagation revealed similar activation patterns and velocities in both groups of mice.
  
  
  CONCLUSIONS
  A sensitive method that accurately measures local CVs throughout the ventricles revealed no changes in Cx43+/- mice, which is consistent with the demonstration that ECG parameter values in the heterozygous mice are the same as those in wild-type mice.
authors.affiliation: Department of Pharmacology, SUNY Health Science Center at Syracuse, New York 13210, USA. morleyg@vax.cs.hscsyr.edu
authors.forename: G E
authors.initials: GE
authors.lastname: Morley
authors.forename: D
authors.initials: D
authors.lastname: Vaidya
authors.forename: F H
authors.initials: FH
authors.lastname: Samie
authors.forename: C
authors.initials: C
authors.lastname: Lo
authors.forename: M
authors.initials: M
authors.lastname: Delmar
authors.forename: J
authors.initials: J
authors.lastname: Jalife
mesh_terms: D000818:Animals; D018031:Connexin 43 / Q000502:physiology*; D004562:Electrocardiography; D006329:Heart Conduction System / Q000503:physiopathology*; D006352:Heart Ventricles / Q000503:physiopathology*; D006579:Heterozygote; D051379:Mice; D018345:Mice, Knockout; D014693:Ventricular Fibrillation / Q000235:genetics / Q000503:physiopathology
chemical_list: D018031:Connexin 43