Glucocorticoid signaling in a rat model of post-traumatic stress disorder

Abstract

Posttraumatic stress disorder (PTSD) is a psychological disorder that develops following exposure to perceived life-threatening trauma. Characteristic features include behavioral changes caused by heightened arousal, including fear and anxiety. Glucocorticoid receptor (GR) hypersensitivity, as defined by strong negative feedback, has been one of the most robust findings of altered HPA axis function in PTSD. In this thesis, we evaluated GR-related changes that were exposed to the three consecutive stressors of the single prolonged stress (SPS) animal model for PTSD. We tested the potential of the GR antagonist RU486 treatment in reversing these stress-induced effects. We found that GR antagonism can normalize some stress-induced parameters. We demonstrated that varying the timing of RU486 administration and evaluation gave different behavioral results and dynamics of gene expression, that revealed complex interactions between stress and RU486 over time. We also tested the GR sensitivity after administered the exogenous corticosterone. Our data suggest the enhanced stress responsiveness after SPS to moderate but not mild stressors and a sensitization of brain GR signaling that extends beyond direct negative feedback regulation. Lastly, we provide evidence for a role of β-arrestin-2 as a modulator of regulating amygdala activity in response to fear/anxious memory of PTSD.