Simultaneously Recorded Oscillations in Membrane Potential and Isometric Contractile Force from Cardiac Muscle

Abstract

IN 1943, Bozler^1,2 reported unusual sinusoidal oscillations in membrane potential and contractile tension which occurred immediately after relaxation of a normally triggered contraction in turtle heart muscles bathed in calcium solutions of high concentrations. Reiter^3–5 observed similar contractile oscillations (which he called “aftercontractions”) in mammalian myocardium in a variety of conditions that enhance contractility. Contractile oscillations have been shown to be unaccompanied by propagated action potentials^4,6. Kaufmann's group, however, detected slow corresponding oscillatory waves in membrane potential similar to those described by Bozler, and they assumed that the contractile oscillations are initiated by electrical oscillations.