Abstract

Cardiac arrest and cardiopulmonary resuscitation (CA/CPR) increase the risk for affective disorders in human survivors. Postischemic anxiety- and depressive-like behaviors have been documented in animal models of CA/CPR; however, the stability of post-CA/CPR anxiety-like behavior over time and the underlying physiologic mechanisms remain unknown. The hypothalamic-pituitary-adrenal (HPA) axis and the corticotropin releasing factor (CRF) system may mediate the pathophysiology of anxiety and depression; therefore, this study measured CA/CPR-induced changes in CRF receptor binding and HPA axis negative feedback. Mice were exposed to CA/CPR or SHAM surgery and assessed 7 or 21 days later. Consistent with earlier demonstrations of anxiety-like behavior 7 days after CA/CPR, increased anxiety-like behavior in the open field was also present 21 days after CA/CPR. On postoperative day 7, CA/CPR was associated with an increase in basal serum corticosterone concentration relative to SHAM, but this difference resolved by postoperative day 21. The Dexamethasone Suppression Test showed that the CA/CPR group had enhanced negative feedback compared with SHAM controls at postoperative day 21. Furthermore, there was a gradual increase in CRF(1) receptor binding in the paraventricular nucleus of the hypothalamus and bed nucleus of the stria terminalis, as well as a transient decrease of both CRF(1) and CRF(2A) receptors in the dorsal hippocampus. Therefore, sustained changes in activity of the HPA axis and the CRF system after CA/CPR may contribute to the postischemic increase in affective disorders.