Mirogabalin alleviates central neuropathic pain: An investigation using a rat model of cervical spinal cord injury without radiographic abnormalities.

CONTEXT: The prevalence of central neuropathic pain (cNeuP) is increasing, particularly in older patients with spinal cord injury (SCI) without radiographic abnormalities resulting from minor external forces. Preclinical research has shown the effectiveness of gabapentinoid treatment for cNeuP after SCI in the spinal cord without stenosis. However, no studies have reported the efficacy of this treatment in models of spinal cord compressive lesions.

OBJECTIVE

To determine the effects of mirogabalin for cNeuP after SCI in a rat model of chronic spinal cord compressive lesions.

METHODS

A model of chronic spinal compressive lesion was created in rats by inserting an expandable water-absorbing polyurethane sheet under the sublaminar space. After 8 weeks, SCI without radiographic abnormalities causing hypersensitivity was induced using an Infinite Horizon Impactor device. The rats with cNeuP were divided into 3 groups: a saline group, a high-dose mirogabalin besylate (MGB) group, and an MGB low-dose group. Pain-related behavior and histology were evaluated for up to post operative 28 days.

RESULTS

Compared with rats in the saline-treated group, those in the MGB-treated groups presented an increased pain threshold. Significant improvement was observed in MGB-treated rats for up to 21 days. Histology and mRNA expression revealed reduced expression of Iba-1 and α2δ-1 in MGB-treated rats.

CONCLUSION

Administration of MGB decreased Iba-1 and α2δ-1 immunoreactivity in the dorsal horns of a rat model of cervical SCI at 4 weeks after injury. The inhibitory effect of MGB on the α2δ-1 subunit after SCI may contribute to the analgesic effect on cNeuP.