Study shows how hormones released after brain injury contribute to movement problems

Hormones released after brain injury contribute to movement problems on the left and right sides of the body, scientists at Uppsala University and elsewhere can now show in a new study in rats. The results also suggest that hormone-blocking treatments may help counter these effects, a finding that has implications for the treatment of people with traumatic brain injuries or strokes. The study was published in eLife.

A stroke or injury to one side of the brain causes difficulty in movement on the opposite side of the body. Scientists once thought this was because nerves on one side of the brain control activity on the opposite side. But recent studies have shown that giving rats without brain damage certain hormones can elicit movement responses similar to human motor deficits on one side of the body.

This has led us to wonder if pituitary hormones might in part mediate the side-specific movement problems that humans may experience after brain injury, ”

Georgy Bakalkin, study co-lead author and professor, Department of Pharmaceutical Biosciences, Uppsala University

To further their research, Bakalkin and his team looked at the effects of unilateral brain injury in rats lacking the connection between the brain and the nerves that regulate the hind limbs. They found that even without this connection, the hind limb on the side opposite the injury had impaired reflexes.

However, animals lacking the pituitary gland, a hormone-producing gland connected to the brain, did not experience these problems. Two pituitary hormones β-endorphin and Arg-vasopressin appeared to play a role. When the team administered these two hormones to rats without brain damage, the rats also developed right-sided hindlimb contraction.

Then they tested what would happen if they gave the rats drugs for left-sided brain damage that block the effects of these two hormones. They found that the animals did not develop movement problems on the right side. This suggests that the hormones transmit specific signals to one side after a brain injury, and that treating patients who have a similar injury with drugs that block the effects of these hormones may be of benefit.

“These observations suggest that the endocrine system through its hormones in the blood can selectively target the left and right sides of the animal body,” Bakalkin concludes. “This is an unusual phenomenon that requires further study and verification in other animal models. We must be careful in interpreting these results and their biological implications before further research. Future studies confirm the benefits of treatments that block these hormones, they may offer a new approach to treat movement problems after stroke or injury. Now that this has been published, we could proceed to analyze the mechanisms under -jacent and the role of this phenomenon in the control of our body plan and in neurological disorders ”.