Opiate Masking of Stress-Induced Hypervigilance: The Cause of Delayed Symptom Presentation in PTSD
Annual rept. 15 Sept 2008 14 Sept 2009
VETERANS BIOMEDICAL RESEARCH INST EAST ORANGE NJ
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The goal of this concept award was to establish different ways of eliciting persistent exaggerated startle responses in rats and to determine whether manipulation of endogenous opiate receptors can disrupt those processes. To date, we have tested 2 different means by which to increase startle reactivity inescapable stress and avoidable stress. A single day versus 3 days of inescapable stress was compared. Three days of inescapable stress caused a delayed increase in startle reactivity, but administration of naloxone, an opiate antagonist, did not cause any appreciable change in the startle following inescapable stress. Avoidable stress also caused a delayed increase in startle reactivity, but the delay was substantially longer than in the inescapable stress paradigm and lasted longer. The appearance of an exaggerated startle response several days following avoidable stress suggests that the appearance of startle exaggeration days following stressor exposure is not likely caused by a specific pain-dependent mechanism as much as some type of coping process.