title: Morphine prevents the development of stress-enhanced fear learning.
abstract: The current study investigates the pharmacotherapeutic use of morphine as a preventative treatment for stress-enhanced fear learning, an animal model that closely mimics symptoms of post-traumatic stress disorder (PTSD). PTSD is a chronic and debilitating anxiety disorder characterized by exaggerated fear and/or anxiety that may develop as a result of exposure to a traumatic event. In this model, rats are exposed to a severe stressor (15 foot shocks) in one environment (Context A) and then subsequently exposed to a milder form of the same stressor (single foot shock) in a different environment (Context B). Animals that did not receive prior shock treatment exhibit fear responsiveness to Context B in line with the severity of the single shock given in this context. Animals that had received prior shock treatment in Context A exhibit an exaggerated learned fear response to Context B. Furthermore, animals receiving a single dose of morphine immediately following the severe stressor in Context A continue to show an enhanced fear response in Context B. However, animals receiving repeated morphine administration (three injections) after exposure to the severe stressor in Context A or a single dose of morphine at 48 h after the severe stressor no longer exhibit an enhancement in fear learning to Context B. These results are consistent with clinical studies suggesting that morphine treatment following a severe stressor may be useful in preventing or reducing the severity of PTSD in at-risk populations.
authors.affiliation: Department of Psychology, University of North Carolina at Chapel Hill, CB#3270, Chapel Hill, NC 27599-3270, USA.
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Szczytkowski-Thomson
authors.forename: Christina L
authors.initials: CL
authors.lastname: Lebonville
authors.forename: Donald T
authors.initials: DT
authors.lastname: Lysle
mesh_terms: D000818:Animals; D003213:Conditioning, Psychological / Q000187:drug effects*; D004195:Disease Models, Animal; D004334:Drug Administration Schedule; D004597:Electroshock / Q000379:methods / Q000523:psychology; D005239:Fear / Q000187:drug effects* / Q000523:psychology*; D008297:Male; D009020:Morphine / Q000008:administration & dosage* / Q000627:therapeutic use*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013313:Stress Disorders, Post-Traumatic / Q000188:drug therapy / Q000517:prevention & control* / Q000523:psychology; D013315:Stress, Psychological / Q000188:drug therapy* / Q000523:psychology; D013997:Time Factors
chemical_list: D009020:Morphine