INFLUOF PASSIVE EXERCISE ON STRETCH REFLEX PROPERTIES IN RATS W/SC INJURY

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Spasticity is an abnormal reflex response to muscle stretch that commonly results in impairment following spinal cord injury (SCI). The loss of supraspinal control due to SCI contributes to the development of this hyperreflexia, but the exact mechanisms have not been elucidated. Insight into the mechanisms of spasticity and the development of more effective treatments are needed to improve the function and quality of life in individuals with SCI. This study proposes a new model for the direct measure of the electromyography (EMG) and joint torque during the imposed stretch of the calf muscles in spinal cord transected rats. The aims of the study are to examine the effects of passive exercise on spasticity and to determine the emergence of spasticity post injury. Although smaller in magnitude, stretch reflexes are present in spinal intact humans and rats. In contrast, normal humans do not have a motor phenomenon called windup of the stretch reflex. This study would present the first evidence of stretch reflex windup in a SCI rat, and the windup behavior will serve as a means to quantify spasticity and make inter-group and longitudinal comparisons that are not possible by standard EMG measurement. The proposed study is designed to allow comparison of a transected control group and a transected group receiving daily passive exercise over an 8 week period. Tests of spasticity will involve 2 separate protocols. The velocity protocol will use 3 different velocities of stretch to document the emergence of stretch reflexes post injury. The windup protocol will use 3 different frequencies to measure the amount of hyperreflexia. Both protocols will be tested on a weekly basis.