Activated Microglia Contribute to the Maintenance of Chronic Pain after Spinal Cord Injury

The Journal of Neuroscience, 2006 · DOI: 10.1523/JNEUROSCI.0003-06.2006 · Published: April 19, 2006

Spinal Cord Injury Neurology Pain Management

Simple Explanation

Spinal cord injuries can lead to chronic pain that is hard to treat. This study explores the role of microglia, a type of immune cell in the spinal cord, in maintaining this chronic pain. Researchers hypothesized that activated microglia contribute to chronic pain after SCI. Rats with spinal cord injuries were treated with minocycline, a drug that inhibits microglia. The treatment reduced the hyper-responsiveness of neurons in the spinal cord and restored normal pain thresholds. When the minocycline treatment was stopped, the pain symptoms returned, indicating that microglia play a crucial role in maintaining the chronic pain after spinal cord injury.

Study Duration

4 weeks

Participants

Adult male Sprague Dawley rats (200–225 g)

Evidence Level

Level II: Animal Study

Key Findings

1
Thoracic spinal cord injury (SCI) in rats causes chronic activation of microglia in the lumbar spinal cord.
2
Activated microglia contribute to the maintenance of neuronal hyperresponsiveness and pain-related behaviors.
3
Inhibition of microglia with minocycline led to a temporary reduction in pain and neuronal hyper-excitability, suggesting microglia's active role in modulating pain after SCI.

Research Summary

This study investigates the role of activated microglia in maintaining chronic pain after spinal cord injury (SCI) in rats. The researchers hypothesized that activated spinal microglia contribute to chronic central pain after SCI. The study found that thoracic SCI causes chronic activation of microglia in the lumbar spinal cord, contributing to neuronal hyperresponsiveness and pain-related behaviors. Minocycline, a microglial inhibitor, temporarily reduced pain and neuronal hyper-excitability. The findings suggest that microglia actively contribute to ongoing pain after SCI, which differs from their role in peripheral nerve injury where they are primarily involved in the induction phase of pain.

Practical Implications

Therapeutic Target

Microglia may represent a therapeutic target for treating chronic pain after spinal cord injury.

Drug Repurposing

Minocycline, an existing drug, may be a potential candidate for treating post-SCI pain.

Further Research

Further studies are needed to understand the role of microglia in the induction and maintenance of chronic pain after SCI.

Study Limitations

1
The study was conducted on rats, and the results may not be directly applicable to humans.
2
The study only examined the role of microglia and did not fully explore the involvement of other glial cells, such as astrocytes.
3
The study focused on the maintenance phase of chronic pain and did not investigate the role of microglia in the initial development of pain after SCI.

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