Effect of Exercise on μ-Opioid Receptor Expression in the Rostral Ventromedial Medulla in Neuropathic Pain Rat Model

Ann Rehabil Med, 2015 · DOI: 10.5535/arm.2015.39.3.331 · Published: June 1, 2015

Simple Explanation

This study investigates how exercise impacts neuropathic pain by examining changes in opioid receptors in a specific brain region of rats. Neuropathic pain is a chronic condition often resistant to treatment, leading to exploration of non-pharmacological methods like exercise. The experiment involved dividing rats into groups: a control group, a group with induced neuropathic pain, and a group with neuropathic pain that underwent regular treadmill exercise. The researchers then measured pain responses and analyzed opioid receptor expression in the rats' brains. The findings suggest that exercise can alleviate neuropathic pain, potentially by reducing the sensitivity of opioid receptors in the brain. This shift in brain circuitry may favor pain inhibition, offering a possible mechanism for how exercise provides pain relief.

Study Duration

4 weeks

Participants

32 male Sprague-Dawley rats

Evidence Level

Not specified

Key Findings

1
Regular treadmill exercise led to a decrease in body weight in the CCI+exercise group compared to the CCI group.
2
Withdrawal thresholds and latencies, indicators of pain sensitivity, increased with time in both the CCI and CCI+exercise groups, with significant differences between these groups after exercise.
3
μ-opioid receptor (MOR) expression was significantly decreased in the RVM and spinal cord of the CCI+exercise group compared to the CCI group.

Research Summary

This study aimed to determine the effects of aerobic exercise on neuropathic pain and whether regular treadmill exercise alters μ-opioid receptor (MOR) expression in the rostral ventral medulla (RVM) in a neuropathic pain rat model. The results indicated that regular treadmill exercise can alleviate neuropathic pain symptoms, with exercised CCI rats showing improved outcomes compared to non-exercised rats. Furthermore, body weights of CCI rats with regular treadmill exercise program for 4 weeks were lower than those of non-exercised rats. The researchers concluded that exercise-induced analgesia in neuropathic pain may be mediated by desensitization of central MOR by endogenous opioids, leading to a shift of RVM circuitry balance towards pain inhibition.

Practical Implications

Non-Pharmacological Pain Management

Exercise can serve as a non-pharmacological intervention for managing neuropathic pain, potentially reducing reliance on medication.

Opioid Dosage Reduction

Combining exercise with opioid analgesics may allow for lower doses of pain medication due to similar mechanisms of action.

Brain Circuitry Understanding

Further investigation using neuroimaging can help elucidate the brain circuitry involved in exercise-induced analgesia.

Study Limitations

1
Further verification requires neuronal recording using microelectrodes.
2
Indirect measurement of increased β-endorphin in peripheral blood and cerebrospinal fluid does not reflect the opioid level in the central nervous system (CNS).
3
There is a lack of information concerning the alteration of central opioid receptor after exercise in neuropathic pain

Your Feedback

Was this summary helpful?

Back to Pain Management