Researchers trigger stress disorder in mice study

Researchers trigger stress disorder in mice study

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
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