Up-Regulation of Pain Behavior and Glial Activity in the Spinal Cord after Compression and Application of Nucleus Pulposus onto the Sciatic Nerve in Rats

Translocation of AMPA Receptors in the Dorsal Horn of the Spinal Cord Corresponding to Long-term Depression Following Pulsed Radiofrequency Stimulation at the Dorsal Root Ganglion

Objective

Pulsed radiofrequency stimulation at the dorsal root ganglion is used for treatment of radicular pain; however, its mechanism for neuropathic pain treatment has not been fully elucidated. Here, we investigated whether pulsed radiofrequency stimulation affects the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors, which play a critical role in synaptic plasticity.

Methods

Neuropathic pain was studied using a radicular neuropathic pain model (43 female Sprague-Dawley rats; 200–250 g). In total, 28 rats were assigned to the following groups for fraction analysis: a control group, a control + pulsed radiofrequency stimulation group, a disc pain group, and a disc pain + pulsed radiofrequency stimulation group. For nonfraction analysis of Glutamate A1 (GluA1) and GluA2 subunits, a total of 15 female Sprague-Dawley rats were assigned to a control group, a disc pain group, and a disc pain + pulsed radiofrequency stimulation group. Pulsed radiofrequency stimulation and subsequent analysis were conducted three days after surgery.

Results

AMPA receptor subunits, GluA1 and GluA2, in the radicular neuropathic pain model were upregulated compared with those in the control group three days after surgery. Pulsed radiofrequency stimulation induced the translocation of GluA1 and GluA2 subunits from the synaptosome to cytosol without a change in the total amount of AMPA receptors in the dorsal horn.

Conclusions

Our results demonstrated that pulsed radiofrequency stimulation affected the synaptic plasticity corresponding to long-term depression. Thus, we show that long-term depression from pulsed radiofrequency stimulation is associated with analgesic effects in the radicular neuropathic pain model following peripheral inflammation.

The Effect of GCSB-5 a New Herbal Medicine on Changes in Pain Behavior and Neuroglial Activation in a Rat Model of Lumbar Disc Herniation

Objective

Lumbar disc herniation can induce sciatica by mechanical compression and/or chemical irritation. The aim of this study was to compare the effects of GCSB-5 (Shinbaro®) and NSAIDs on pain-related behavior and on the expressions of microglia, astrocytes, CGRP, TRPV1, IL-6, and CX3CL1 in a rat model of lumbar disc herniation.

Methods

112 male Sprague-Dawley rats underwent implantation of nucleus pulposus to a dorsal root ganglion (DRG). Rats were divided into five groups as follows; a saline group (the vehicle control group) (n=27), a 10 mg/kg aceclofenac group (the aceclofenac group) (n=22), and 100, 300 or 600 mg/kg GCSB-5 groups (the GCSB-5 100, 300, or 600 groups) (n=21 for each group). Rats were tested for mechanical allodynia at 3 days after surgery and at 1 day, 3 days, 7 days, 14 days, 21 days, 28 days, 35 days, 42 days, 49 days, and 56 days after treatment commencement. Immunohistochemical staining of microglia (Iba1), astrocytes (GFAP), CGRP, and TRPV1, and PCR for IL-6 and CX3CL1 were performed on spinal dorsal horns and DRGs at 56 days after medication commencement.

Results

After 56 days of GCSB-5 300 administration, mechanical withdrawal thresholds were significantly increased (p<0.05), and immunohisto-chemical expressions of Iba1, GFAP, CGRP, and TRPV1 were reduced than other groups, but this difference was not statistically significant.

Conclusion

These results indicate GCSB-5 reduces mechanical allodynia and downregulates neuroglial activity and the expressions of CGRP and TRPV1 in the spinal segments of a rat model of lumbar disc herniation.