Electrophysiological characteristics of rodent myocardium damaged by adrenaline

Myocardial cell injury was produced in rats and guinea pigs by injecting 3.0 mg.kg-1 1-adrenaline subcutaneously. Ventricular myocardium removed from animals 24 h after the injection exhibited marked electrophysiological alterations when studied in vitro. These alterations included: (1) reduced resting membrane potential, action potential amplitude and duration, and dV/dt; (2) conduction disturbances such as delay, unidirectional block, summation and inhibition; (3) abnormal automatic activity including triggered sustained rhythmic activity and post-overdrive acceleration. Conduction disturbances were affected by stimulus intensity, duration, rate and site of pacing. Isoprenaline (10(-7) mol.litre-1) improved conduction. Automatic activity was modified by changes in entrance and exit block and depolarising or hyperpolarising current pulses. These data indicate that diverse abnormal electrophysiological alterations occur in myocardium damaged by adrenaline.