Borgens 9631560 Spinal cord injuries are devastating to those that survive them, producing lifelong losses in important bodily functions. The loss of function is in part due to a break in the nerve fibers from the spinal cord to the brain, and those that carry impulses from the brain to various parts of the body. One possible means to restore this "two-way" impulse conduction is to induce and guide the regeneration of nerve fibers around or through the area of injury. Such regeneration does not normally happen in mammals, but occurs naturally in other vertebrates, usually leading to functional recovery after spinal cord injury. A novel means to accomplish this task is to impose a weak voltage across the injury site. This approach arises from very clear evidence that the application of this electrical field can both initiate and direct the growth of fibers; this has been shown in studies of nerve cells grown in culture, as well as in various "whole animal" studies (for example in the spinal cord of primitive fish and guinea pigs). Nerve processes grow towards the negative pole, and degenerate away from the positive pole of the applied voltage. Weak applied voltages may also induce a predictable orientation of other cells important to the injury process such as astrocytes, that form scar tissue in the spinal cord, and macrophages, which also play a prominent role in acute injury. To be clinically useful, an applied voltage must influence nerve processes projecting in both directions within the spinal cord. Since growth response towards the negative pole are immediate, and degenerative responses occurring at the positive pole occur much later, the direction of the applied voltage can be reversed every 15 to 30 minutes to produce nerve growth in both directions. This is called oscillating field stimulation (OFS). OFS has produced significant levels of functional recovery in naturally injured paraplegic dogs in veterinary clinical trials. An implantab le OFS unit is now in development for the first trial in human patients; however, before human clinical trials may begin, more information must be gathered on the effects of OFS in other mammals. Up to this point, experiments involving laboratory rats and guinea pigs have been limited due to the large size of the prototype OFS device. In this study, the investigators will use a recently developed miniaturized OFS device, combined with a hand-held sensor to test the function of the unit from outside the body, to determine the mechanisms of action, target cells and critical aspects of this new technology.
