ACUTE SOCIAL STRESS AND CARDIAC ELECTRICAL-ACTIVITY IN RATS

This paper summarizes the results of experiments aimed at describing e lectrocardiographic responses to different acute social stressors in h ealthy male rats. Electrocardiograms were telemetrically recorded duri ng maternal aggression, social defeat, and psychosocial stimulation, a s obtained using the classical resident-intruder paradigm. Autonomic i nput to the heart was indirectly evaluated by means of heart rate vari ability measures and plasma catecholamine level determinations. Social stressors produced changes in cardiac electrical activity that were m arkedly higher than those observed in nonsocial challenging conditions such as novelty and restraint. Defeat, which produced the highest cat echolaminergic responses, was the most potent as a social aversive exp erience in inducing heart rate accelerations and arrhythmias, particul arly when applied to a wild-type strain of rats. The far most frequent arrhythmic events were ventricular and supraventricular premature bea ts, either as isolated events or grouped. Ventricular premature beats usually occurred immediately after attacks and in association with hig her heart rate values and lower heart rate variability scores. The rel ationships between the type of stressor used (either social or nonsoci al), the different contributions of the emotional and physical compone nts of stress response, the resulting modulation of autonomic control over cardiac electrical activity, and the incidence of arrhythmic even ts are discussed. (C) 1998 Wiley-Liss,Inc.