Analgesic Effect of SKI306X on Chronic Postischemic Pain and Spinal Nerve Ligation-Induced Neuropathic Pain in Mice

Neuropathic pain (NP) results from lesions or diseases affecting the peripheral or central somatosensory system. However, there are currently no drugs that are particularly effective in treating this condition. SKI306X is a blend of purified extracts of three oriental herbs (Clematis mandshurica, Trichosanthes kirilowii, and Prunella vulgaris) commonly used to treat osteoarthritis for their chondroprotective effects. Chronic postischemic pain (CPIP) and spinal nerve ligation (SNL) models were created by binding the upper left ankle of mice with an O-ring for 3 h and ligating the L5 spinal nerve, respectively. Mice with allodynia were injected intraperitoneally with 0.9% normal saline (NS group) or different doses (25, 50, or 100 mg/kg) of SKI306X (SKI groups). We assessed allodynia using von Frey filaments before injection and 30, 60, 90, 120, 180, and 240 min and 24 h after injection to confirm the antiallodynic effect of SKI306X. We also measured glial fibrillary acidic protein (GFAP) levels in the spinal cord and dorsal root ganglia to confirm the change of SKI306X administration. Both models exhibited significant mechanical allodynia. The intraperitoneal injection of SKI306X significantly increased the paw withdrawal threshold in a dose-dependent manner, as the paw withdrawal threshold was significantly increased after SKI306X administration compared with at baseline or after NS administration. GFAP levels in the SKI group decreased significantly (p < 0.05). Intraperitoneal administration of SKI306X dose-dependently attenuated mechanical allodynia and decreased GFAP levels, suggesting that GFAP is involved in the antiallodynic effect of SKI306X in mice with CPIP and SNL-induced NP.