title: Inhibitory effect of tetrahydropalmatine on calcium current in isolated cardiomyocyte of guinea pig.
abstract: OBJECTIVE
  To study the effect of tetrahydropalmatine (THP) on calcium channels in ventricular single cells of guinea pig heart.
  
  
  METHODS
  Patch-clamp technique (whole cell recording) was used to observe calcium current in ventricular myocytes.
  
  
  RESULTS
  THP decreased ICa in ventricular myocytes with a dose and frequency-dependent manner. THP (0.1, 1, and 10 mumol.L-1) decreased ICa from 1.15 +/- 0.22, 0.91 +/- 0.18, and 1.60 +/- 0.42 nA (control) to 0.9 +/- 0.21 (P < 0.01), 0.56 +/- 0.21 (P < 0.01), and 0.83 +/- 0.21 nA (P < 0.05), respectively, number of cells is five in each group (n = 5), and the rates of the depression of ICa were 22%, 38%, and 48%, respectively. The effect was easily reduced by washing the cell with the Tyrode's solution. The current-voltage relation curve showed that the potential producing peak value of ICa was 0 mV at which THP had the most markedly inhibited action on ICa. When the stimulating frequency was changed, ICa varied in a frequency-dependent manner 5 min after THP was given, and the inhibition of THP was stronger at 2 Hz than that at 0.1 Hz.
  
  
  CONCLUSIONS
  THP possessed a Ca2+ channel blocking effect.
authors.affiliation: Department of Physiology, Harbin Medical University, China.
authors.forename: C
authors.initials: C
authors.lastname: Xu
authors.forename: M Z
authors.initials: MZ
authors.lastname: Sun
authors.forename: Y R
authors.initials: YR
authors.lastname: Li
authors.forename: B F
authors.initials: BF
authors.lastname: Yang
authors.forename: L J
authors.initials: LJ
authors.lastname: Wang
authors.forename: J M
authors.initials: JM
authors.lastname: Li
mesh_terms: D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D001600:Berberine Alkaloids / Q000494:pharmacology*; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D015220:Calcium Channels / Q000187:drug effects*; D002478:Cells, Cultured; D006168:Guinea Pigs; D006352:Heart Ventricles; D009206:Myocardium / Q000166:cytology*; D018408:Patch-Clamp Techniques
chemical_list: D001600:Berberine Alkaloids; D002121:Calcium Channel Blockers; D015220:Calcium Channels; C014215:tetrahydropalmatine