Grant: Operating Grant

Although many components involved in movements like walking are known to change with advanced age, little is known of how these individual changes combine to affect movement. For example, while studies have separately reported changes with aging in muscle fibers, spinal motoneurons, spinal locomotor circuits, and transmission of sensory information, in several models, the combined effects of these changes on movement are unknown. In addition the effects of a regular mild, combined endurance and resistance exercise program, begun in middle age when age-related changes begin to manifest themselves, on this locomotor system are unknown. In the proposed research, there are 4 aims. In aim 1, we will investigate, in rats, how aging (up to the equivalent of 90 yrs in humans) influences the properties of spinal neurons and their innervated muscle fibers, when activated together as occurs during movement. In aim 2, spinal cord locomotor patterns will be measured in response to stimulation of a center in the brainstem which evokes locomotor behavior through activation of spinal circuits. In aim 3, we will examine age-associated changes in the expression of genes important for cellular function, in motor and sensory nerve cells of the hind limb. In aim 4, the effects of a regular exercise program that combines endurance-type (voluntary exercise wheel) and resistance-type (grid-climbing) exercise on the age-related changes found in the above aims will be determined, when the exercise program is initiated at a time when age-associated changes have begun to express themselves. The results will inform us as to the effects of aging on the locomotor system as a whole, as well as on its constituent parts. The results will also help inform us as to the use of exercise as a therapeutic tool during the aging process, to offset the locomotor deficits resulting from aging.