Most people gradually recover from trauma, but a small fraction of individuals develop post-traumatic stress disorder (PTSD) — prompting scientists to look for the biological underpinnings of this extreme response to traumatic situations such as warfare, car accidents and natural disasters. Research published on 11 August in Proceedings of the National Academy of Sciences identifies up to 334 genes that may be involved in vulnerability to post-traumatic stress in rats.
Most animal studies of stress use intense stimuli such as electric shocks, designed to produce large, group differences between exposed and unexposed animals. But Nikolaos Daskalakis and his colleagues tried a subtler approach to elicit a wide range of individual responses in rats that had all experienced the same trauma — more closely mimicking the variability of human responses to disturbing events. “We wanted to capture the differences between a susceptible individual and one that is not susceptible to the same experience,” says Daskalakis, a neuroendocrinologist at the Icahn School of Medicine at Mount Sinai in New York.
To probe the mechanisms that control trauma susceptibility, the researchers used DNA microarray technology to screen 22,000 genes in samples from the blood, and the amygdala and hippocampus — brain areas that are involved in fear and memory. In males and females, and across the different tissues, anywhere from 86 to 334 genes showed changes in expression levels that appeared to relate to extreme or minimal responsiveness. “It gives us insight into a genetic marker for PTSD susceptibility and potential treatments targeting activation of the glucocorticoid receptor as a part of therapy,” says David Diamond, a behavioural neuroscientist at the University of South Florida in Tampa. Finding better indicators for trauma susceptibility could help researchers to develop and monitor treatments, he says.