Title: Adaptive muscle plasticity of a remaining agonist following denervation of its close
نویسندگان
چکیده
27 Complete spinal cord injury (SCI) alters the contractile properties of skeletal muscle and 28 although exercise can induce positive changes, it is unclear if the remaining motor system can produce 29 adaptive muscle plasticity in response to a subsequent peripheral nerve injury. To address this, the 30 nerve supplying the lateral gastrocnemius and soleus muscles was sectioned unilaterally in four cats 31 that had recovered hindlimb locomotion following spinal transection. In these spinal cats, kinematics 32 and electromyography (EMG) were collected before and for 8 weeks after denervation. Muscle 33 histology was performed on the lateral (LG) and medial (MG) gastrocnemii bilaterally in four spinal 34 and four intact cats. In spinal cats, cycle duration for the hindlimb ipsilateral or contralateral to the 35 denervation could be significantly increased or decreased compared to pre-denervation values. Stance 36 duration was generally increased and decreased for the contralateral and ipsilateral hindlimbs, 37 respectively. The EMG amplitude of MG was significantly increased bilaterally following denervation 38 and remained elevated 8 weeks post-denervation. In spinal cats, the ipsilateral LG was significantly 39 smaller than the contralateral LG whereas the ipsilateral MG weighed significantly more than the 40 contralateral MG. Histological characterizations revealed significantly larger fiber areas for Type IIa 41 fibers of the ipsilateral MG in three of four spinal cats. Microvascular density in the ipsilateral MG was 42 significantly higher than the contralateral MG. In intact cats, no differences were found for muscle 43 weight, fiber area or microvascular density between homologous muscles. Therefore, the remaining 44 motor system after complete SCI retains the ability to produce adaptive muscle plasticity. 45
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