Terrifying events appear to change the structure of the brain, and a better understanding of the process could help doctors curb the harmful effects of post-traumatic stress disorder. Researchers at the University of New Mexico received a $2.8 million grant this summer from the National Institute of Mental health to study what happens inside the brain when we experience or witness a traumatic event.
But first, they will need to freak out a mouse.
Researchers plan to expose genetically engineered mice to a smell that mice know means danger, said Dr. Elaine Bearer, lead researcher for the project. In this case, researchers use a fox pheromone that mice recognize as a predator.
The smell had a similar effect on researchers, she said.
“You just felt like your hair stood on end,” said Bearer, a professor of pathology and neurosurgery at the UNM School of Medicine. “There’s something built into us to respond to this pheromone.”
After exposing the mice to the pheromone, researchers will use magnetic resonance imaging to view the effect of the trauma in the mouse’s brain.
The brain “lights up” during a trauma, and the effects are visible using MRI, Bearer said. In some individuals, among both mice and men, brain activity quiets down rapidly, while in others activation is prolonged.
“We think in a person who does get PTSD, (the brain) doesn’t deactivate,” Bearer said. “It continues. And that continuance causes circuitry changes, anatomical changes, that we can see” in MRI images.
Prolonged brain activity appears to lead to permanent changes in brain structure that play a role in the development of PTSD, Bearer said.
A chief goal of the five-year study is to advance understanding about the disease itself and how it progresses, which today remains somewhat mysterious, she said.
Over the next year, Bearer and others plan to repeat the “predator exposure” experiment with four groups of mice that have been genetically engineered to show varying responses to fear.
Some of the mice have received a human gene that may play a role in our ability to tolerate stress.
Another goal of the study is to learn whether our genes make us more or less vulnerable to PTSD, Bearer said.
“We don’t know if these genes give humans a different response to stress, and that’s one of the things we’re studying,” she said.
PTSD was first diagnosed in 1980 and prevalence rates are unclear, but the illness has been widely diagnosed among returning combat veterans who received traumatic brain injuries as a result of roadside bombs.
An estimated 2,461 veterans of the Iraq and Afghanistan wars treated for PTSD at the New Mexico VA Health Care System between October 2001 through June 30, according to a report issued last month by the Department of Veterans Affairs.
The report found that nearly 30 percent of the 834,463 veterans of the Iraq and Afghanistan wars treated at VA hospitals and clinics nationwide have been diagnosed with PTSD.
Better understanding of PTSD could lead to therapies that help the brain relax after trauma, heading off harmful effects of the illness.
Past research has shown that some drugs given to trauma patients in the first hours after the injury may interrupt the progression of PTSD.
Bearer noted that a 2010 study published in the New England Journal of Medicine found that severely injured military personnel who received morphine as part of trauma care were significantly less likely to develop PTSD than those who did not receive the drug.
Down the road, Bearer wants to design studies with trauma patients transported to the UNMH emergency room in search of therapies that cut the odds that a patient will develop PTSD.
But doctors probably have only a limited window to help the brain calm down before the harm becomes permanent.
“Once the circuitry changes happen, deactivation isn’t going to help,” she said.
Later treatment typically relies on psychotherapy, she said.