Effects of thiopental on contractile and electrophysiological properties of single canine left ventricular cells.
The effects of thiopental on contraction, membrane potential and membrane ionic currents were studied in single canine left ventricular cells. Thiopental 10(-5) and 10(-4) mol/l reduced the cell-shortening from 7.02 +/- 0.64 microns to 5.66 +/- 1.39 and 3.48 +/- 0.64 microns respectively (mean +/- S.D., N = 10, 0.5 Hz). This effect was enhanced in higher (> 1.0 Hz) electrical stimulation frequencies. Also, thiopental decreased the plateau phase and shortened the duration of action potential. On the other hand, voltage clamp experiment revealed that thiopental 10(-6), 10(-5), and 10(-4) mol/l reduced peak Ca2+ current from 520 +/- 48 pA to 387 +/- 60 pA, 261 +/- 84 pA, and 84 +/- 36 pA respectively (mean +/- S.D., N = 8), and showed a use-dependent block of Ca2+ current. However, only a high dose of thiopental (10(-4) mol/l) inhibited the Na+ current. We conclude that the negative inotropic effect of thiopental on the heart is mediated mainly via inhibition of the Ca2+ current.
Kubo
H
H
Department of Anesthesiology, Faculty of Medicine, Toyama Medical and Pharmaceutical University, Japan.
Hatakeyama
N
N
Satone
T
T
Shibuya
N
N
Ito
Y
Y
Yamamura
S
S
Momose
Y
Y
D000818:Animals; D004285:Dogs; D006321:Heart / Q000187:drug effects* / Q000502:physiology; D006352:Heart Ventricles / Q000166:cytology / Q000187:drug effects; D006993:Hypnotics and Sedatives / Q000494:pharmacology*; D066298:In Vitro Techniques; D009200:Myocardial Contraction / Q000187:drug effects*; D018408:Patch-Clamp Techniques; D013874:Thiopental / Q000494:pharmacology*
D006993:Hypnotics and Sedatives; D013874:Thiopental