To demonstrate that there are indeed parasympathetic responses in the skeleton, the researchers injected a weakened rabies virus into the thigh bones of mice. The rabies virus has a unique feature -- it migrates from its injection site in the periphery along nerve fibers towards the brain. Following injection to the thigh bone, the virus was found in the brain in regions known to be specific for the parasympathetic subsystem.
In the past, these same researchers reported that the activity of a protein called interleukin-1 influences bone development. Now they noticed that this influence is very similar to that of the parasympathetic subsystem. Indeed, the researchers showed that deactivating interleukin-1 activity in the brain of laboratory mice paralyzes parasympathetic activity in the bone and slows down skeletal development. They further found that the newly discovered neuronal pathway, which includes interleukin-1 in the brain and the parasympathetic subsystem, also controls the heart rate.
As in the bone and the heart, the new pathway might have an important function as well in other organs controlled by the autonomic nervous system. Prof. Yirmiya said that "low bone density and osteoporosis often appear together with neuropsychiatric disorders such as depression, Alzheimer's disease and epilepsy, since interleukin-1 in the brain and the parasympathetic system are often damaged in these disorders. Finding the disease mechanisms in these cases has a huge potential for the development of new therapies," he added.
"The connection between the brain and the bone in general and the involvement of the newly discovered pathway in particular is a new area of research about which we still know very little," said Prof. Bab. "The new findings, discovered in our Hebrew University laboratories, highlight for the first time an important physiologic role for the connection be
|Contact: Jerry Barach|
The Hebrew University of Jerusalem