VOA慢速英语2014 科学家研发PTSD血液测试（在线收听）

AS IT IS 2014-08-25 Scientists Developing Blood Test for PTSD

Post-Traumatic Stress Disorder or PTSD is caused by a frightening event, either witnessed or experienced.  Signs of the disorder may include depression, bad dreams and severe nervousness.  Thoughts about the event may be uncontrollable.

Soldiers who have seen a lot of death and destruction in armed conflict, survivors of natural disasters and rape victims often suffer from PTSD. 

Even with treatment, the brain disorder is difficult to cure.  But someday, a blood test may show if a person is threatened by PTSD or already suffers from it.  Researchers at Icahn School of Medicine at Mount Sinai in New York have identified a blood marker that appears linked to PTSD.

The researchers used rats and cat waste in their work.  They saw a pattern of gene activity involved in the operation of the stress hormone corticosterone in the brain tissue of the rats.  The activity took place after the rats smelled the urine of cats for 10 minutes.  The liquid waste was in cat litter, a material that lines a waste box for indoor cats. 

Loud noises caused the rats to show anxiety - fear - when they were tested.  And they were easily startled.  Then, the stressed rats were given corticosterone an hour after they smelled the cat litter.  The researchers found that one week after seeing the litter, the treated rats showed little interest and nervousness compared to untreated rats.

Icahn scientist Nikolaos Daskalakis said Swiss doctors noted that the hormone corticosterone calmed people who received it after a car accident.  He said the finding may lead to the development of a test for PTSD risk.  The test would measure what is called glucocorticoid receptor activity in the blood.  The receptors are genes that become "turned on" in the presence of stress.

Corticosterone is produced naturally by the body.  The hormone connects to the receptor and has a calming effect.  But in some rats and in some people, the pathway appears to be ineffective.  This puts them at higher risk for PTSD. 

Scientist Daskalakis says PTSD does not just affect the brain.  He says it involves the whole body.  He says this is why identifying common regulators is extremely important.  He also says more detailed studies in humans and in animals are needed in order to one day have a treatment.