Blunted Corticosterone Response to Acute Predator Stress Results in Long-Term Spatial Memory Impairment

Abstract

SOJ Psychology Open Access Research Articlepituitary-adrenal (HPA) axis response to a traumatic event could affect his or her likelihood of developing PTSD [8][9][10]. In these studies, researchers showed that individuals who developed PTSD exhibited significantly lower levels of cortisol after the traumatic event than those individuals who did not develop PTSD. Preclinical work has provided similar results by examining the development of PTSD-like behaviors in different strains of rats. For instance, Cohen and colleagues [11] reported that Lewis rats, which exhibit a significantly blunted corticosterone response to stress, are more prone to developing PTSD-like behaviors following an acute stressor than Fischer or SpragueDawley rats. However, the studies conducted on this topic thus far have not been able to determine whether it is the HPA axis response to an acute stressor that affects PTSD / PTSD-like behavior development or if reduced HPA axis activity is merely a baseline characteristic of the people / rats that are more likely to develop PTSD / PTSD-like behaviors.Only one study of which we are aware has utilized an experimental inhibition of a rat's HPA axis response to stress in order to assess whether or not it would facilitate the development of PTSD-like behaviors. In that study, the investigators found that the combination of a blunted corticosterone and parasympathetic nervous system response to stress resulted in significantly greater anxiety on an elevated plus maze three weeks following a single stress exposure [12]. However, these results were observed when comparing the experimental groups to their respective controls only, and the effects of the manipulations on cognitive performance were not examined. This latter point is especially important because PTSD can be considered a disorder of memory, as individuals suffering from the disorder show marked impairments of learning and memory, a phenomenon that may be a result of intrusive memories transiently interfering with these individuals' ability to process new information [13][14][15][16][17]. Thus, the purpose of the present study was to determine whether or not a blunted HPA axis response to acute predator