A hormone known to affect appetite may also play a role in making the brain vulnerable to stress, according to a new study in rats.
The findings suggest ghrelin could actually predispose people to post-traumatic stress disorder, said researchers from the Massachusetts Institute of Technology, and that identifying ways to decrease ghrelin could potentially protect high-risk people from developing the condition.
"Perhaps we could give people who are going to be deployed into an active combat zone a ghrelin vaccine before they go, so they will have a lower incidence of PTSD," study researcher Ki Goosens, an assistant professor of brain and cognitive sciences at the university, said in a statement. "That's exciting because right now there's nothing given to people to prevent PTSD."
The study is published in the journal Molecular Psychiatry. Researchers gave rats a ghrelin receptor-stimulating drug, or gene therapy to increase the expression of a growth hormone produced in the amygdala. Ghrelin increases production of this growth hormone in the amygdala in the face of stress.
Both these things increased fear susceptibility in the rats, which was determined by the amount of time they remained "frozen" after hearing a tone they were trained to fear. Meanwhile, blocking the receptors for the growth hormone or ghrelin decreased fear back to normal levels among stressed rats.
In addition, researchers found that exposing rats to chronic stress for a long period of time was linked with increased levels of growth hormone and circulating ghrelin.