Sensory Afferents Regenerated into Dorsal Columns after Spinal Cord Injury Remain in a Chronic Pathophysiological State

Exp Neurol, 2007 · DOI: 10.1016/j.expneurol.2007.05.013 · Published: August 1, 2007

Spinal Cord Injury Regenerative Medicine Physiology

Simple Explanation

This study examines the functional status of sensory axons that have regenerated after a spinal cord injury (SCI). Researchers stimulated axon regrowth using a peripheral nerve conditioning lesion combined with antibodies that block growth-inhibitory effects. Six months post-injury, the regenerated axons were located, and their electrical activity was measured. The study found that these regenerated axons had reduced conduction velocity, decreased ability to follow high-frequency stimuli, and increased latency to repetitive stimuli. Many of these regenerated axons were also found to be chronically demyelinated. These findings indicate that regenerated sensory axons after SCI remain in a chronically impaired state.

Study Duration

6-8 months post-SCI

Participants

Adult Sprague Dawley rats

Evidence Level

Not specified

Key Findings

1
Regenerated axons had reduced conduction velocity compared to intact axons.
2
The regenerated sensory axons exhibited decreased frequency-following ability, indicating impaired transmission of high-frequency signals.
3
Many regenerated axons were chronically demyelinated, which likely contributes to their impaired functional properties.

Research Summary

The study investigates the physiological properties of regenerated sensory axons in the dorsal columns after spinal cord injury (SCI) in rats. It was found that regenerated axons, six months post-injury, exhibit pathophysiological conduction properties, including reduced conduction velocity, decreased frequency-following ability, and increased latency to repetitive stimuli. The study also found evidence of chronic demyelination in many of the regenerated axons, suggesting a need for therapeutic strategies to restore normal functional properties to regrowing axons.

Practical Implications

Therapeutic Strategies

The study highlights the need to develop therapeutic strategies to restore normal conduction properties to regenerated axons after spinal cord injury, focusing on remyelination.

Chronic Phase Interventions

The finding that surviving and regenerated axons are electrically excitable even months after injury suggests that treatments applied during the chronic phase of SCI may be effective.

Functional Recovery Mechanisms

The observation that regenerated sensory axons remain in a chronic pathophysiologic state raises questions about the role of these fibers in the functional recovery often observed in animal models of SCI, suggesting other mechanisms may contribute.

Study Limitations

1
The study focuses on sensory axons in rats and may not directly translate to humans.
2
The study does not address the synapse formation of regenerated sensory axons with their targets in the brainstem.
3
It is not known how much of the reduced CV is due to slower conduction along the regenerated axon segment or due to delays as the thinner regenerated segment transitions into the undamaged segment.

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