A group of researchers from University College London (UCL) and the University of Zurich, discovered that doxycycline —an antibiotic commonly used to treat bacterial infections, such as acne, urinary intestinal infections, eye, gonorrhea, chlamydia, and others— can disrupt the formation of negative associations in the brain. Therefore, it may help treating posttraumatic stress disorder (PTSD).

The study consisted of giving volunteers the antibiotic or placebo (control group) randomly; and inducing in them an association between a color and an electric shock. For this, they were showed either blue or red in a computer, and 50 percent of the times one of the colors appeared, they received a painful electric shock.

In a second session, the participants were shown the colors again, but this time there were not electric shocks. Instead, a loud sound played every time after either color was shown. The objective was to measure their fear memory response, done by tracking their eye blinks and compare the difference between the color previously associated with the shock (bad color) and  the other (good color).

The results showed that the memory fear response was 60% lower in participants who were administered the antibiotic, while it did not affected other cognitive measures (like sensory memory and attention).

Lead author Dominik Bach, professor and researcher at UCL explained: “When we talk about reducing fear memory, we are not talking about deleting the memory of what actually happened. […] The participants may not forget that they received a shock when the screen was red, but they ‘forget’ to be instinctively scared when they next see a red screen. Learning to fear threats is an important ability for any organism, helping us to avoid dangers such as predators. Over-prediction of threat, however, can cause tremendous suffering and distress in anxiety disorders such as PTSD.”

“We have demonstrated a proof-of-principle for an entirely new treatment strategy for PTSD. The theory is based on the recent discovery that our brains need proteins outside nerve cells, called matrix enzymes, to form memories. Matrix enzymes are found throughout the body, and their over-activity is involved in certain immune diseases and cancers. To treat such diseases, we already have clinically approved drugs that block these enzymes, including the antibiotic doxycycline, so we wanted to see if they could help to prevent fear memories from forming in the brain. Our results support this theory, opening up an exciting avenue of research that might help us to find treatments for PTSD,” he added.

“Using drugs to prevent PTSD would be challenging, since in the real world we don’t know when a traumatic event is about to occur. However, there is growing evidence that people’s memories and associations can be changed after the event when they experience or imagine similar situations. This is called ‘reconsolidation’, and we now plan to test the effect of doxycycline on reconsolidation of fear memories. If this is successful, we would hope to apply the technique to more clinically realistic models of PTSD within a few years,” the expert concluded.

 

Source: UCL News