Publication date: Dec 02, 2019
Credit: CC0 Public Domain Long-term (chronic) treatment with opioids, such as morphine, prior to trauma enhances fear learning in mice, according to a study published in Neuropsychopharmacology.
The findings, which link chronic opioid treatment before a traumatic event with responses to subsequent stressful events, may suggest a possible mechanism underlying the frequent co-occurrence of post-traumatic stress disorder (PTSD) and opioid dependence.
Using an established model of fear learning in mice, researchers at the University of California, Los Angeles, USA assessed the potential impact of chronic opioid treatment on subsequent development of PTSD-like behaviors.
On the subsequent day, mice from both the trauma and non-trauma groups were transferred to a new environment and exposed to a mild stressor (a milder foot shock), before being returned to that environment for eight minutes on the fourth day of the experiment.
The authors also tested treating mice with opioids after the initial trauma had occurred but before exposing them to the second, mild stressor.
They found that mice treated with morphine after the initial trauma did not show enhanced fear learning following exposure to the mild stressor.
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