[The effect of propranolol on the myocardial force-length relationship in the in situ canine left ventricle].
The effect of beta-adrenoceptor blockade on the wall performance of the in situ canine left ventricle (LV) was evaluated based on the LV end-systolic force-diameter (Fes-Des) relation in 10 healthy mongrel dogs. LV diameter was measured with ultrasonic crystals, and LV pressure was measured with a micromanometer. Preload was altered by inferior vena caval (IVC) occlusion. In the control contractility state, the IVC was occluded for 7 sec. Blockade of the cardiac beta-adrenergic nerves was induced with 2 mg/kg propranolol i.v.. Slopes (Ec) and extrapolated diameter intercepts (D(o)) of the LV Fes-Des relation were obtained from end-systolic data of the control contractility state and after the infusion of propranolol. Ec was used as an index for the inotropic state of the myocardium of the LV wall. IVC occlusion during 7 sec under the control contractility state produced little change in the heart rate. Thus, IVC occlusion for 7 sec avoided the major reflex change of autonomic tone. After the infusion of propranolol, the heart rate and Ec both decreased by 24 and 43% of the control value, respectively; whereas, D(o) was not significantly altered. Therefore, it was suspected that the cardiac beta-adrenergic nerve played an important role in maintaining myocardial contractility state of the in situ canine LV wall.
Yoshihara
T
T
Department of Medicine, Dokkyo University School of Medicine, Tochigi.
Takeda
K
K
Kadota
R
R
Nakamura
Y
Y
Yagi
S
S
D000320:Adrenergic Fibers / Q000187:drug effects / Q000502:physiology; D000818:Animals; D004285:Dogs; D006321:Heart / Q000187:drug effects / Q000294:innervation; D008955:Models, Cardiovascular; D009200:Myocardial Contraction / Q000187:drug effects*; D011433:Propranolol / Q000494:pharmacology*; D016277:Ventricular Function, Left / Q000187:drug effects*
D011433:Propranolol