January 17, 2014. Memories of major physical or psychological trauma, such as combat or abuse, often persist for years and can lead to anxiety disorders such as post-traumatic stress disorder (PTSD). A new study in mice suggests that a class of drugs called histone deacetylase inhibitors, when given in combination with behavioral therapy, may be useful in helping people with PTSD reduce the emotionally upsetting aspects of old memories, reports a new study published January 14 in Cell.
Li-Huei Tsai and colleagues at the Massachusetts Institute of Technology in Boston trained mice to associate hearing a tone with receiving a painful shock. After repeated pairings, hearing even just the tone alone made the mice fearful. One month later, they trained the mice to unlearn, or “extinguish,” this traumatic memory by repeatedly playing the tone without the shock. This type of training is the mouse version of a psychological technique called exposure therapy that is often used to treat PTSD.
Although extinction could banish the fear for 24 hours, one month later the mice again were frightened by hearing the tone—similar to how a traumatic memory generates anxiety years later in a person with PTSD. Giving a histone deacetylase inhibitor prior to the extinction training prevented the fear from returning, a finding that may provide a foundation for new treatments for PTSD and other anxiety disorders. (For more details, see the related news story.)—Allison A. Curley.