Flight or Fight Reaction Triggered By Bones Not Adrenaline

"In bony vertebrates, the acute stress response is not possible without osteocalcin," said Gérard Karsenty, MD, Ph.D., chair of the Department of Genetics and Development at Columbia University Vagelos College of Physicians and Surgeons and the senior investigator on the study in a news release. "It completely changes how we think about how acute stress responses occur."

Researchers have proven bones are more than calcified tubes

For a long time, researchers viewed bones as calcified tubes but work by Karsenty over the years showed the skeleton has influence over other organs in the body. Through his research, we learned the skeleton releases osteocalcin, which goes through the bloodstream and impacts the functions of the brain, muscles, pancreas and other organs in the body. Studies conducted more recently have demonstrated that osteocalcin helps regulate metabolism. 

Since bones already protect organs from danger--the skull keeps the brain safe from trauma-- it's not a stretch that they will allow vertebrates to escape from danger. 

Mice freak out when presented with predator urine

In order to confirm that theory, the researchers gave mice predator urine and other stressor and then studied the bloodstream to detect changes. In about two to three minues the osteocalcin level increased as did heart rate, body temperature and blood glucose levels as the fight or flight reaction kicked off. In humans, the researchers found osteocalcin increases when they have to speak in public or are cross-examined and are stressed out about it.

Mice who were genetically engineered to not produce osteocalcin didn't have a reaction at all. "Without osteocalcin, they didn't react strongly to the perceived danger," Karsenty says. "In the wild, they'd have a short day."