title: Cytochalasin D as excitation-contraction uncoupler for optically mapping action potentials in wedges of ventricular myocardium.
abstract: BACKGROUND
  Cytochalasin D in tissue bath superfusate inhibits the contraction of isolated thin trabeculae from canine right ventricle without affecting the intracellular action potential recorded with glass microelectrode. The purpose of this study was to test whether cytochalasin D could also be used to immobilize perfused wedges of ventricular muscle without affecting the action potential duration or propagation, and also to determine the optimal concentration and time duration of drug in the perfusate.
  
  
  RESULTS
  Using a membrane potential sensitive dye, di-4-ANEPPS, and a high-resolution photodiode optical mapping system at a rate of 1,000 frames/sec, we recorded action potentials on the transmural surface of arterially perfused wedges of muscle from the canine left ventricular free wall. We also recorded arterial pulse pressure as a surrogate for tissue contraction. Cytochalasin D at > or = 20 micromol/L in the perfusate for > or = 6 minutes reduced the arterial pulse pressure to approximately one tenth of its initial value and significantly reduced or eliminated motion artifacts in the action potentials. A sustained concentration of 10 micromol/L cytochalasin D in the perfusate prevented contraction from recurring after the tissue was immobilized with an initial concentration of 25 micromol/L. Cytochalasin D had little effect on the action potential duration and on its transmural gradient, and did not slow the transmural velocity of excitation propagation.
  
  
  CONCLUSIONS
  Cytochalasin D can be used to uncouple excitation and contraction in perfused canine cardiac muscle for the fluorescent-optical mapping of action potentials without affecting action potential duration or slowing transmural propagation.
authors.affiliation: Krannert Institute of Cardiology, Indiana University Medical School, Indianapolis, USA. jiaswu@iupui.edu
authors.forename: J
authors.initials: J
authors.lastname: Wu
authors.forename: M
authors.initials: M
authors.lastname: Biermann
authors.forename: M
authors.initials: M
authors.lastname: Rubart
authors.forename: D P
authors.initials: DP
authors.lastname: Zipes
mesh_terms: D000200:Action Potentials / Q000187:drug effects* / Q000502:physiology; D000818:Animals; D003326:Coronary Circulation / Q000187:drug effects; D015638:Cytochalasin D / Q000494:pharmacology*; D004285:Dogs; D004594:Electrophysiology / Q000379:methods; D005456:Fluorescent Dyes; D006321:Heart / Q000187:drug effects* / Q000502:physiology*; D009200:Myocardial Contraction / Q000187:drug effects* / Q000502:physiology; D055095:Optics and Photonics; D012107:Research Design; D014475:Uncoupling Agents / Q000494:pharmacology*; D016276:Ventricular Function / Q000187:drug effects
chemical_list: D005456:Fluorescent Dyes; D014475:Uncoupling Agents; D015638:Cytochalasin D