Sanguinarine Attenuates Neuropathic Pain in a Rat Model of Chronic Constriction Injury

Objective. There is still no effective treatment of neuropathic pain. Sanguinarine is a natural plant medicine with anti-inflammatory effects, but its effect on neuropathic pain remains unclear. This study was aimed at investigating the potential of sanguinarine to attenuate neuropathic pain. Methods. Neuropathic pain was induced by chronic constriction injury (CCI) of the sciatic nerve. Rats were randomly divided into several groups: sham, CCI, CCI+SG (1.00 mg/kg), CCI+SG (2.50 mg/kg), and CCI+SG (6.25 mg/kg). SG was injected intraperitoneally from the day of surgery every three days. The mechanical withdrawal threshold (MWT) and thermal withdrawal latency (TWL) were recorded before surgery and on days 1, 3, 7, and 14 after surgery. The microglia in the spinal dorsal horn were examined by immunofluorescence. p38 MAPK expression in the spinal dorsal horn was detected by PCR and Western blot analysis. Cytokine levels in the spinal dorsal horn were measured by ELISA. Results. MWT and TWL were significantly reduced in the CCI group, but sanguinarine recovered MWT and TWL in the CCI group. In addition, sanguinarine inhibited the activation of microglia and decreased the expression of p-p38 and TNF-alpha, IL-1 beta, and IL-6 in the spinal dorsal horn of the CCI group in a dose-dependent manner. Conclusions. Our results suggest that sanguinarine can attenuate neuropathic pain via inhibiting the activation of microglia and the activation of the p38 MAPK signaling pathway.