2003 Director's Summary Synopsis

NEUROPHYSIOLOGY APPROACHES FOR RESTORING MOVEMENT
Christine K. Thomas, Ph.D. • Brian R. Noga, Ph.D.

In addition to repairing spinal cord anatomy (structural components like neurons and axons), researchers must also understand and restore function. Spinal cord physiology deals with the functions or activities of nerve cells. By studying the properties of different types of nerve-nerve and nerve-muscle interactions, researchers gain a clearer understanding of the physiological approaches to restore movement.

In previous studies, Dr. Christine Thomas has used embryonic spinal cord cells to replace neurons that die after spinal cord injury. Those studies showed that these replacement cells are able to make connections to muscles that had lost their nerve supply. In her recent study, she was interested in determining the properties of the muscle fibers that responded to the transplanted cells. Interestingly, she found the transplanted cells established a connection with the more fatigue-resistant muscle fibers. Future studies need to enhance survival of more of these particular neurons, not only to retain the fatigue-resistance of the muscles but also to improve muscle strength.

Another physiological approach to restore movement may come from a better understanding of how neurons in the brain interact with neurons in the spinal cord. The spinal neurons that are important for walking are particularly sensitive to the neurotransmitter, norepinephrine. Neurons in the brain release norepinephrine where their nerve endings meet the neurons in the spinal cord. In his study to measure the release of norepinephrine within the spinal cord during stimulation of the brain, Dr. Brian Noga characterized how norepinephrine affects the activity of spinal neurons. The results of this study may help in the design of a therapy to provide norepinephrine to the spinal cord, thereby affecting the activity of the spinal neurons and potentially improving walking after SCI.

Synopsis Publications

 Thomas CK, Sesodia S, Erb DE, Grumbles RM (2003) Properties of medial gastrocnemius motor units and muscle fibers reinnervated by embryonic ventral spinal cord cells. Exp Neurol 180:25-31.

 Hentall ID, Mesigil R, Pinzon A, Noga BR (2003) Temporal and spatial profiles of pontine-evoked monoamine release in the rat's spinal cord. J Neurophysiol 89:2943-2951.