title: [Electrophysiologic study of the biphasic effects of cyclovirobuxine D on arrhythmias].
abstract: OBJECTIVE
  To explore the possible mechanism of cyclovirobuxine D (CVB-D) in countering and inducing arrhythmia, by way of studying its electro-physiological effect on ventricular papillary muscles of rats in vitro.
  
  
  METHODS
  The transmembrane potential of rat's isolated right ventricular papillary muscles were recorded using conventional glass micro-electrode technique.
  
  
  RESULTS
  (1) CVB-D in concentration of 13.3-63.3 micromol/L, showed prolonging effect on the action potential repolarization time, mainly the action potential duration 50 (APD50), APD70 and APD90, in dose-dependent manner, in concentration of 33.3-63.3 micromol/L, it could inhibit the resting potential, action potential amplitude (APA) and maximum depolarization velocity (Vmax) in dose-dependent manner. (2) CVB-D also showed time-dependent effect, the effect initiated 10 min after 20 micromol/L was perfused in ventricular muscle, the APD50, APD70 and APD90 were potentiated gradually along with prolongation of action time and reached the peak at 30-40 min, without any potentiation thereafter. (3) CVB-D could markedly prolong the effective refractory period (ERP) of action potential, increase the ratio of ERP/APD. (4) CVB-D in concentration of 33.3 micromol/L could induce frequent, multifocal spontaneous arrhythmia in some cells when the action time was longer than 45 min.
  
  
  CONCLUSIONS
  CVB-D has the action of anti-ventricular arrhythmia, the mechanism is correlated with the prolongation of APD and ERP of ventricular muscle as well as the increase of ERP/APD ratio, while it also has the effect of inducing arrhythmia, the mechanism might be concerned with excessive prolongation of APD and the inhibition on RP, APA and Vmax.
authors.affiliation: Department of Cardiology, The First Affiliated Hospital of Medical College, Zhejiang University, Hangzhou (310003).
authors.forename: Zhang-qiang
authors.initials: ZQ
authors.lastname: Chen
authors.forename: Shen-jiang
authors.initials: SJ
authors.lastname: Hu
authors.forename: Wei-ya
authors.initials: WY
authors.lastname: Shi
authors.forename: Juan
authors.initials: J
authors.lastname: Du
authors.forename: Yueliang
authors.initials: Y
authors.lastname: Shen
authors.forename: Qiang
authors.initials: Q
authors.lastname: Xia
mesh_terms: D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D000889:Anti-Arrhythmia Agents / Q000494:pharmacology*; D001145:Arrhythmias, Cardiac / Q000139:chemically induced* / Q000503:physiopathology; D004365:Drugs, Chinese Herbal / Q000494:pharmacology*; D022062:Electrophysiologic Techniques, Cardiac; D006352:Heart Ventricles / Q000187:drug effects*; D066298:In Vitro Techniques; D008297:Male; D032383:Myocytes, Cardiac / Q000166:cytology; D010210:Papillary Muscles / Q000187:drug effects; D051381:Rats; D017207:Rats, Sprague-Dawley; D012032:Refractory Period, Electrophysiological / Q000187:drug effects; D016276:Ventricular Function
chemical_list: D000889:Anti-Arrhythmia Agents; D004365:Drugs, Chinese Herbal; C032939:cyclovirobuxine D