For decades, scientists have known that nerve cells in the brain communicate with each other through high-speed contacts called synapses. Now, researchers at Oregon Health Sciences University's Vollum Institute and the University of Oxford have discovered that synapses also are used to communicate with other specialized brain cells called oligodendrocytes. Studying these previously unknown synapses may provide a key for understanding brain function in health and disease. These results appear in the May 11 edition of the journal Nature.
Oligodendrocytes produce myelin, a sheath that surrounds and insulates nerve fibers. This insulation allows nerve fibers to transmit signals at high speed, like the signals from the spinal cord to the leg muscles. The breakdown of myelin around these nerve fibers is believed to be the cause of multiple sclerosis.
Scientists at OHSU, in collaboration with colleagues at the Medical Research Council Unit at Oxford, have found that the oligodendrocytes taking part in this communication are in their immature stage and do not produce myelin. Previous work has shown that glutamate, the chemical used to transmit signals at these synapses, can inhibit the development of these cells into the mature, myelin-producing oligodendrocytes. These newly discovered connections may help answer many remaining questions about how nerve cells regulate myelin formation.
While the research team stresses their basic science finding is years away from providing treatment options for MS patients, they hope to continue building on this work to further understand the beneficial and detrimental nerve communications that take place in the brain.
"It is our hope that continued research will lead to treatments that will stimulate the maturation of these immature oligodendrocytes to allow re-myelination to occur after injury or disease," said Dwight Bergles, Ph.D., a postdoctoral fellow at OHSU and lead author of the paper. "However, it is likely that we still face years of research before this work travels from the scientist's bench to the patient's bedside."
Researchers used two separate techniques to discover these connections. OHSU scientists recorded the tiny electrical signals generated at the synapses between nerve cells and oligodendrocytes. Their collaborators in the MRC Unit at Oxford, professor Peter Somogyi, Ph.D., D.Sc., and J. David B. Roberts used an electron microscope to see the cell junctions, or synapses, where the nerve signals are being transmitted.
"Scientists are just beginning to understand the processes through which cells of the brain communicate with one another," said Craig Jahr, Ph.D., a senior scientist at OHSU's Vollum Institute and co-author of the study. "In the future, we hope to learn more about what happens when these lines of communication are broken and what we can do to repair them or prevent further damage."
This work was supported by funds from the National Institutes of Health and the Medical Research Council, United Kingdom.
Journal
Nature