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. Highlights We utilize the stress-enhanced fear learning (SEFL) model of PTSD. -Repeated morphine administration following trauma blocks SEFL -Single morphine injection given immediately following trauma has no effect on SEFL. -A single morphine injection given 48-hours after the trauma block SEFL -Morphine may be an effective preventative therapy for populations at-risk for PTSD.
Szczytkowski-Thomson, Jennifer L.; Lebonville, Christina; and Lyslea, Donald, "Morphine prevents the development of stress-enhanced fear learning" (2013). Psychology Educator Scholarship. 35.