Corticosterone as a Predictor of Long-term Outcomes of Fear Attenuation Treatment

Abstract

Blunted adrenal corticosteroid levels and dysregulation of the Hypothalamic Pituitary Adrenal (HPA) Axis are known risk factors for developing PTSD (Delahanty et al., 2000; McFarlane et al., 1997). Although other risk factors for PTSD and disorders involving conditioned fear exist, Kimble et al. (in preparation) have suggested that CS preexposure may serve as a protective measure against fear development and relapse of conditioned fear in an animal model. Although the mechanisms are not entirely clear, research has suggested that preexposure may change the activity of the HPA axis. For example, rats repeatedly exposed to a cue prior to fear conditioning exhibit more HPA activation than animals that were not preexposed to the cue, as evidenced by elevated heart rate and blood pressure (e.g., Zhang et al., 2004). Here, we attempted to determine whether CS preexposure affects HPA axis activity as measured through circulating corticosterone (Experiment 1) and if depressing the HPA axis through dexamethasone alters the CS preexposure effect.