Antinociceptive effect of ethanolic extract of Bauhinia brachycarpa Benth on neuropathic pain model induced by partial sciatic nerve ligation.

Ethnopharmacological Relevance: The plant Bauhinia brachycarpa Benth (BBB) has been traditionally used for treating muscle aches such as bone pain, and neuralgia for a long time, on account of its sedative and antinociceptive activities in Yunnan province of China. However, there was no experimental evidence to confirm its traditional medicinal use.

Aim Of The Study: The antinociceptive effect and possible mechanism of ethanolic extract of BBB on neuropathic pain was evaluated through a model of partial sciatic nerve ligation in mice.

Materials And Methods: A commonly employed animal model induced by partial sciatic nerve ligation (PSNL) in mice was established in the aim of studying neuropathic pain. Ethanolic extract of BBB (1000, 500, 250 mg/kg) and pregabalin (60 mg/kg) were intragastric administrated daily for 7 days post-PSNL. Mechanical and thermal hyperalgesia were assessed throughout the experimental period. After the experiment, the levels of tumor necrosis factor-α (TNF-α) and interleukin-10 (IL-10) in serum were determined by ELISA. The mRNA expressions of ionized calcium binding adaptor molecule 1 (Iba-1), CD16, CD206, arginine-1 (Arg-1), interleukin-1β (IL-1β), and inducible nitric oxide synthase (iNOS) in the spinal cord were detected by qPCR. The protein levels of Iba-1, CD16, CD206, and p38 phosphorylation in the spinal cord were detected by immunohistochemistry and western blotting. The phytochemical analysis of BBB was performed through the colorimetric test.

Results: Neuropathic pain induced by PSNL was significantly alleviated by BBB treatment, which decreased pro-inflammatory cytokines such as TNF-α, IL-1β and iNOS, increased anti-inflammatory cytokine such as IL-10 and Arg-1, and attenuated p38 phosphorylation. BBB also reduced the number of Iba-1 and CD16 positive cells, but it enhanced the number of CD206 positive cells. n-Butanol portion that was partitioned from the ethanolic extract had the highest content of total flavonoids among all the portions, and the antinociceptive effect of n-butanol portion is better than that of other portions.

Conclusions: Our findings indicate that the antinociceptive effect of BBB is mediated by inhibiting the inflammatory response and regulating the differentiation of microglia. The antinociceptive effect of BBB was related to the content of total flavonoids.