MedicalResearch.com Interview with: Dominik R Bach, PhD, MD University of Zurich MedicalResearch.com: What is the background for this study? What are the main findings? Response: Posttraumatic stress disorder (PTSD) can occur after a psychological trauma such as physical violence, abuse, or natural disaster. It is characterised by increased arousal, flashbacks, and nightmares that reflect memories of the trauma. Current therapies include talking therapy, but it is costly and does not work in everybody. This is why we were looking for ways of reducing aversive memories with a drug. In the current study, we found that the antibiotic doxycycline impairs the formation of negative memories in healthy volunteers. To form memories, the brain needs to strengthen connections between neurons. It has recently emerged that for strengthening such connections particular proteins are required that sit between nerve cells, so-called MMPs. They are involved in many disorders outside the brain, such as certain cancers and heart disease. This is how we already know that doxycycline suppresses the activity of MMPs. Since doxycycline is relatively safe and readily accessible, our research was relatively straightforward. 76 healthy volunteers - half women, half men - came to the laboratory and received either placebo (a sugar pill) or 200 mg doxycycline. They then took part in a computer test in which one screen color was often followed by a mildly painful electric shock and another color was not. A week later, volunteers came back to the lab. They were shown the colors again , this time followed by a loud sound but never by shocks. The loud sounds made people blink their eyes - a reflexive response to sudden threat. This eye blink response was measured. Volunteers who had initially been under placebo had stronger eye blink after the color that predicted electric shock than after the other color. This "fear response" is a sensitive measure for memory of negative associations. Strikingly, the fear response was 60% lower in participants who had initially taken doxycycline.