Abstract
AbstractAlthough most spinal cord injuries are anatomically incomplete, only limited functional recovery has been observed in people and rats with partial lesions. To address why surviving fibers cannot mediate more complete recovery, we evaluated the physiological and anatomical status of spared fibers after unilateral hemisection (HX) of thoracic spinal cord in adult rats. We made intracellular and extracellular recordings at L5 (below HX) in response to electrical stimulation of contralateral white matter above (T6) and below (L1) HX. Responses from T6 displayed reduced amplitude, increased latency and elevated stimulus threshold in the fibers across from HX, beginning 1-2 weeks after HX. Ultrastructural analysis revealed demyelination of intact axons contralateral to the HX, with a time course similar to the conduction changes. Behavioral studies indicated partial recovery which arrested when conduction deficits began. These findings suggest a chronic pathological state in intact fibers and necessity for prompt treatment to minimize it.
Highlights
Most spinal cord injuries are anatomically incomplete, only limited functional recovery has been observed in people and rats with partial lesions
The major finding from this research is that hemisection at T10 reduces transmission from the contralateral white matter above the hemisection to target cells in the lumbar spinal cord
The deficits in conduction/ transmission for fibers running through the segment that had been hemisected contralaterally did not develop immediately after hemisection, but only after 1-2 weeks
Summary
Most spinal cord injuries are anatomically incomplete, only limited functional recovery has been observed in people and rats with partial lesions. To study the time-related changes in transmission across the hemisection, we measured the intracellular synaptic response in lumbar L5 MNs on both the left (lesioned) or right (intact) sides, evoked by electrical stimulation of the ipsilateral or contralateral VLF at T6 (above the HX), and/or at L1 (below the HX).
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