Application of the Rat Grimace Scale as a Marker of Supraspinal Pain Sensation after Cervical Spinal Cord Injury

JOURNAL OF NEUROTRAUMA, 2017 · DOI: 10.1089/neu.2016.4665 · Published: November 1, 2017

Spinal Cord Injury Neurology Pain Management

Simple Explanation

This study investigates a way to measure pain in rats after a spinal cord injury using the Rat Grimace Scale (RGS). The RGS looks at facial expressions to determine pain levels. Traditional methods of measuring pain in animals rely on withdrawal responses, but these may not accurately reflect the experience of pain, especially after spinal cord injury. The RGS offers a way to assess pain that is processed in the brain. The study found that the RGS can be used to measure both spontaneous pain (pain without a trigger) and evoked pain (pain caused by a stimulus like cold) in rats after a cervical spinal cord injury.

Study Duration

5 weeks

Participants

Adult male Sprague-Dawley rats (n = 15)

Evidence Level

Not specified

Key Findings

1
Rats with spinal cord injuries showed significantly higher RGS scores at week 5 post-injury compared to baseline and control groups, suggesting spontaneous neuropathic pain.
2
The RGS scores increased significantly after the application of acetone, indicating that the RGS can detect supraspinal pain sensation in response to a cold stimulus.
3
A strong correspondence was found between elevated RGS scores and paw withdrawal responses to a cold stimulus, suggesting that both measures together indicate a robust pain response.

Research Summary

This study demonstrates that the Rat Grimace Scale (RGS) can be effectively used to assess supraspinal pain sensation in rats following cervical spinal cord injury (SCI). The RGS was found to be sensitive to both spontaneous and evoked neuropathic pain. The researchers observed a significant increase in RGS scores in SCI rats compared to control groups, indicating the presence of spontaneous pain. Moreover, the RGS scores also increased after the application of a cold stimulus, suggesting that the RGS can detect evoked pain. The study also revealed a correspondence between elevated RGS scores and paw withdrawal responses, which highlights the potential of using both measures to provide a comprehensive assessment of pain in SCI models.

Practical Implications

Improved Pain Assessment

The RGS provides a non-invasive method for assessing pain, including spontaneous pain, which is often overlooked in animal models.

Understanding Pain Mechanisms

The study helps elucidate the relationship between supraspinal and spinal reflex responses to pain stimuli after SCI.

Therapeutic Development

The RGS can be used to evaluate the effectiveness of analgesic interventions in preclinical models of SCI-induced neuropathic pain.

Study Limitations

1
Evaluation of RGS and withdrawal responses at only one time point post-SCI.
2
Sensory threshold testing was not performed.
3
Affective changes such as fear and anxiety could contribute to the behavioral changes observed in the RGS.

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