Involvement of Opioid Peptides in the Analgesic Effect of Spinal Cord Stimulation in a Rat Model of Neuropathic Pain

Neurosci. Bull., 2022 · DOI: https://doi.org/10.1007/s12264-022-00844-7 · Published: April 9, 2022

Simple Explanation

Spinal cord stimulation (SCS) is a technique where electrical impulses are delivered to the spinal cord to alleviate chronic pain. This study investigates how SCS affects neuropathic pain in rats, specifically looking at the role of opioid peptides. The study found that SCS-induced pain relief is influenced by the intensity of stimulation and the severity of the initial pain. Also, the pain-relieving effects of SCS appear to involve the release of certain endorphins, which then activate opioid receptors in the spinal cord. Different frequencies of SCS (2 Hz, 100 Hz, and 10 kHz) activate different opioid receptors, suggesting that SCS can be tailored to activate specific pain-relieving pathways. The pain relief from SCS was found to be sustained without tolerance over a 24-hour period.

Study Duration

Not specified

Participants

138 male Sprague Dawley rats

Evidence Level

Level II: Animal study

Key Findings

1
The analgesic effect of SCS is more effective in rats with moderate, rather than severe, mechanical hypersensitivity.
2
SCS at different frequencies (2 Hz, 100 Hz, and 10 kHz) engages different opioid receptors: 2 Hz activates MOR and KOR, 100 Hz activates KOR, and 10 kHz activates MOR, DOR, and KOR.
3
Continuous SCS stimulation for 24 hours resulted in sustained analgesia without tolerance, suggesting different underlying mechanisms compared to electroacupuncture.

Research Summary

This study characterized the analgesic effect of spinal cord stimulation (SCS) in a rat model of neuropathic pain, focusing on the involvement of opioid peptides. The study explored the impact of stimulation intensity, frequency, and the severity of mechanical hypersensitivity on SCS-induced analgesia. Key findings indicate that the effectiveness of SCS is influenced by the severity of neuropathic pain and that different stimulation frequencies engage distinct opioid receptors (MOR, DOR, and KOR). SCS at 2 Hz increased methionine enkephalin content in the cerebrospinal fluid. Unlike electroacupuncture, SCS-induced analgesia was maintained without tolerance over 24 hours, implying different underlying analgesic mechanisms. These findings contribute to a better understanding of SCS mechanisms and could help optimize its clinical application.

Practical Implications

Personalized SCS Therapy

Tailoring SCS frequency to activate specific opioid receptors could enhance pain relief for individual patients.

Optimizing Stimulation Parameters

Adjusting stimulation intensity based on the patient's level of mechanical hypersensitivity may improve treatment outcomes.

Combination Therapies

Combining SCS with other pain management strategies that target different mechanisms may provide more comprehensive pain relief.

Study Limitations

1
The study was conducted on a rat model, and the results may not directly translate to humans.
2
Only one specific neuropathic pain model (SNI) was used, limiting the generalizability to other pain conditions.
3
The neurochemical mechanisms of newer SCS stimulation patterns were not investigated.

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