Researchers trigger stress disorder in mice study

Published: Thursday, February 29, 1996

By Jennifer K. Morita

Daily Bruin Staff

Researchers at the UCLA Neuropsychiatric Hospital have developed the first animal model of Post-Traumatic Stress Disorder, revealing that repeated reminders of a traumatic event trigger symptoms.

The study was conducted jointly by UCLA psychiatrists and researchers in the department of psychiatry at Olive View Medical Center, according to spokesperson Warren Robak.

Post-Traumatic Stress Disorder (PTSD) is a syndrome that develops after a person experiences a traumatic event like an earthquake or some type of violence, explained Ronald Ritzmann, an Olive View Medical Center researcher who worked with UCLA psychiatrists to develop the animal model.

"When there's a traumatic event ... only a certain percentage of individuals will develop Post-Traumatic Stress Disorder," Ritzmann said. "After a big event, everybody is shook up. Some will recover and some will get progressively worse.

"There's no way to predict who will or will not develop the disorder," Ritzmann added.

According to Alan Steinberg, the symptoms of the disorder can include intrusive thoughts and images of the traumatic event, jumpiness and nervousness.

Ritzmann, Steinberg and UCLA psychiatrists Robert Pynoos developed the animal model to help target people who might need counseling and treatment for the disorder.

Using laboratory mice, researchers exposed the animals to a 10-second, low-amperage electrical shock to simulate a traumatic experience. Researchers exposed some of the mice to reminders of the electrical shock repeatedly over a period of six weeks by placing them in an area next to where they received the shock.

Instead of exploring, the mice tended to stay in a corner, and researchers said they observed the mice breathing more heavily.

"They definitely remember and did not like what happened," Steinberg said. "The amazing findings were that if we took some mice and shocked them but did not expose them to reminders, basically not too much happened with them. They went back to normal.

"But the mice who were reminded had a lot of abnormalities," said Steinberg, adding that one thing that contributes to the persistence of post traumatic stress disorder symptoms is repeated exposure to reminders of the traumatic event.

The mice were also given an acoustic startle test that measured their body reaction to loud noise.

"The mice who were exposed to reminders showed an exaggerated magnitude of startle reaction," Steinberg said. "They were much more reactive to noise and other mice. With PTSD we see people becoming really jumpy after a loud noise."

Researchers also exposed mice to an elevated plus maze, where mice were put on elevated platforms in which some sides are closed in and others are open. Here too, the mice who were exposed to reminders reacted differently from those who weren't.

"They really were abnormal," Steinberg said. "Mice don't like to be high up. They did either of two things. Some became excessively fearful and just stayed inside the closed areas, and some became really fearless and stayed out there too much."

The animal model also revealed something researchers weren't expecting, according to Steinberg. In between testing periods, the mice were kept in cages along with other mice, and watched by veterinarians at the Olive View Medical Center.

"They became excessively aggressive," Steinberg said. "They got into bad fights with serious injuries, maiming and some even died."

Steinberg said this corresponds to reports of some Vietnam War veterans, who after being exposed to combat, displayed increased aggression. Ultimately, researchers hope to use this model to test possible drugs and treatment methods for the disorder, Ritzmann said.

"There is no good treatment right now, no drug that seems to work," he said, adding that counseling is the traditional treatment for post traumatic stress disorder.

"Animal models are useful for screening drugs that will work," Ritzmann said.

One drug company is coming out with a new treatment that Ritzmann said seems to have some benefits.

"We're trying to get them to let us try it, but they're not terribly interested because the drug is already in clinical trial," said Ritzmann. "We're still talking with them."Comments to webmaster@db.asucla.ucla.edu