Social stress, autonomic neural activation, and cardiac activity in rats

Animal models of social stress represent a useful experimental tool to inve stigate the relationship between psychological stress, autonomic neural act ivity and cardiovascular disease. This paper summarizes the results obtaine d in a series of experiments performed on rats and aimed at verifying wheth er social challenges produce specific modifications in the autonomic neural control of heart rate and whether these changes can be detrimental for car diac electrical stability. Short-term electrocardiographic recordings were performed via radiotelemetry and the autonomic input to the heart evaluated by means of time-domain heart rate variability measures. Compared to other stress contexts, a social defeat experience produces a strong shift of aut onomic balance toward sympathetic dominance, poorly antagonized by vagal re bound, and associated with the occurrence of cardiac tachyarrhythmias. Thes e effects were particularly severe when a wild-type strain of rats was stud ied. The data also suggest that the cardiac autonomic responses produced by different types of social contexts (dominant-subordinate interaction, domi nant-dominant confrontation, social defeat) are related to different degree s of emotional activation, which in turn are likely modulated by the social rank of the experimental animal and the opponent, the prior experience wit h the stressor, and the level of controllability over the stimulus. (C) 199 9 Elsevier Science Ltd. All rights reserved.