Corley, Michael Jay2016-03-092016-03-092011-12http://hdl.handle.net/10125/101370M.A. University of Hawaii at Manoa 2011.Includes bibliographical references.PTSD is characterized by stress-induced changes that precipitate debilitating behavioral symptoms including indelible fear memories, hypervigilance, and hyperarousal. Current animal models of PTSD do not adequately capture the spectrum of behavioral symptoms. Hence, this thesis examines whether stress-induced conditioned and sensitized fear memories precipitate extinction and habituation resistant PTSD-like fear behavior. Rats were exposed to three intensities (0.0, 0.4, and 0.8 mA) of footshock stress-induced auditory fear conditioning training pairing auditory clicks with cat odor, followed by five consecutive days of extinction testing in a runway with hide box apparatus (Experiment 1). 0.4 mA and 0.8 mA stress-induced fear conditioned rats exhibited extinction resistant fear behavior characterized by sustained increases in hiding, freezing, and head out behavior. This persistent fear behavior is attributed to the retrieval of a stress-enhanced conditioned fear memory because Experiment 2 indicated that withholding the auditory CS presentation during testing did not produce significant effects or elevations in fear behavior. Of further relevance, stress exposure induces a sensitized state, which is a hallmark symptom of PTSD. Hence, to evaluate whether acute stress induces a habituation resistant sensitized fear state, rats were exposed to differing intensities (0.0, 0.4, and 0.8 mA) of acute footshock stress and tested for habituation to a nonassociative auditory click for five consecutive days (Experiment 3). Stress-sensitized rats showed habituation resistant fear behavior characterized by initial enhanced freezing, transitioning into increased head out behavior, and persisting with elevated locomotion behavior. A companion experiment (Experiment 4) revealed rats did not exhibit sensitized fear behavior in the absence of the nonassociative cue. Taken together, results demonstrate a major role of stress in regulating the persistence of conditioned and sensitized fear memories and provides a relevant model of hallmark PTSD behavioral symptoms.engPTSDThesis