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Social Factors Influence Physiology After Cardiac Arrest

Animal study shows poorer physical/behavioral response in isolated mice

WEDNESDAY, Sept. 8 (HealthDay News) -- In a mouse model of cardiac arrest/cardiopulmonary resuscitation (CA/CPR), mice that had been socially isolated had a worsened physiologic state post-resuscitation than non-isolated mice, according to a study published online Aug. 30 in the Proceedings of the National Academy of Sciences.

Greg J. Norman, of The Ohio State University in Columbus, and colleagues conducted a study of the effect of social isolation on physiological and behavioral response to cerebral ischemia using a well-validated mouse model. One group of mice was kept isolated before undergoing CA/CPR, while another group of mice was kept in a paired environment before the procedure. The mice were then subjected to one of three conditions: surgical control (sham), an ischemic control that did not sustain neuronal damage (hypothermic CA/CPR), or the criterion group (normothermic CA/CPR).

The researchers found that CA/CPR resulted in the increased proinflammatory cytokines tumor necrosis factor-α, interleukin-1β (IL-1β), and IL-6, as well as the microglia marker MAC-1 in all of the mice; however, expression of each of these factors, except IL-6, was increased more in the socially isolated mice. The socially isolated mice exposed to CA/CPR also had significantly higher levels of neuronal cell death on day seven than non-isolated mice, and exhibited more depressive-like behavior and cardiac autonomic dysregulation. In mice that did not have ischemic damage (hypothermic CA/CPR group), the isolated mice and non-isolated mice showed no significant differences in neuronal cell death, autonomic cardiac control, or behavior.

"This study establishes that social environment strongly affects the physiological and behavioral responses to global cerebral ischemia," the authors write. "Physical contact is likely the critical neuroprotective component of social interaction in the current study."

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