Abstract
A direct inotropic effect of CT 1341, a new steroid intravenous anesthetic, upon the myocardium was studied in isolated heart muscles of dogs by measurements of force-velocity relation. CT 1341 at the concentrations over 0.139ml/100ml caused a dose-dependent leftward shift of the force-velocity curve. The maximum velocity of muscle shortening at zero load (Vmax) was decreased progressively with increasing concentration of CT 1341. The values of Vmax at the concentrations of 0.139ml/100ml, 0.279mg/100ml and 0.556ml/100ml were 94.2%, 86.5% and 67.9% of the control, respectively. Peak force, maximum rate of force development and time to peak force during isometric contraction also showed a dose-dependent decrease. Isotonic net shortening, power and work on the heart muscle were decreased dose-dependently at any given load levels. These results suggest that CT 1341 exerts a direct negative inotropic effect on the myocardium. However, the values of Vmax were 98.6% and 94.2% of the control at the concentrations of 0.056ml/100ml and 0.139ml/100ml, which were considered approximately to be the range of blood concentration at the clinically recommended induction doses (0.04-0.1ml/kg). Therefore, the negative inotropic effect of CT 1341 upon the myocardium seems to be minor when it is used within the range of these doses.
