Characterization of two types of inotropic actions on the heart «in vivo»
AbstractArchives Internationales de Physiologie et de Biochiniie, 1972, 80, 145- I52 145 Reqi le 29 septembre 1971. CHARACTERIZATION OF TWO TYPES OF INOTROPIC ACTIONS ON THE HEART (( IN VIVO )) BY N . SEGAL-SHTIGLITZ, I. M. LEVINCER and J. KEDEM (Departmenr of Lye Sciences, Bar-Ilun University, Rumat Can, Israel). The inotropic actions of heart rate and paired stimulation have previously been studied with the aid of curves describing the time et and course of restitution of contractility (KEDEM al., 1969; ROGEL MAHLER,1970). This method, first described by BRAVENY and KRUTA (1958), seems to be a useful tool for analysis of inotropism. In the present study this approach was used to characterize the inotropic mechanisms of various common interventions which augment myocardial contractility. MATERIALS METHODS AND Nineteen mongrel dogs were anaesthetized by intravenous adrninistration of sodium pentobarbital (30 mg/kg). Under artificial respiration (Bird respirator), the chest was opened by longitudinal sternal split, and hook electrodes were placed in the right ventricular muscle close to the apex. Atrioventricular conduction block was produced by electrocoagulation of the A-V node. Isometric tension was recorded from a Walton-Brodie strain-gauge arch sutured to the right ventricular wall, parallel and close to the septum.