Ethnopharmacological relevance: In the practice of traditional Chinese medicine, endometriosis is believed to be caused by blood stasis and is characterised by dysmenorrhea, which is difficult to control. Shi Xiao San has a long history of use in the treatment of gynaecological diseases. The prescriptions composed of Shi Xiao San include Typhae Pollen and Faeces Trogopterori, both of which have anti-inflammatory activity. In addition, Typhae Pollen can be used to treat many kinds of blood stasis diseases.
Aim of the study: The purpose of the present study was to investigate the effect of Shi Xiao San on pain relief in rats with endometriosis and to preliminarily explore its mechanism of action in alleviating pain.
Material and methods: Ten rats received sham operation as the Sham group, and 30 endometriosis model rats were randomly divided into three groups: the Model, Shixiao San-Low (Shi Xiao San-L), and Shixiao San-High (Shi Xiao San-H) groups. The rats were administered the appropriate treatment via intragastric gavage for 4 weeks.
The thermal radiation pain and mechanical pain thresholds of the rats were measured every 7 days after treatment. Finally, the distribution density of nerve fibres in endometrial tissue, the inflammatory infiltration of the dorsal root ganglion (DRG), the expression of TRPV1 in the dorsal root ganglion, and the expression of IL-1β, TNF-α, and IL-6 in ectopic tissue were measured.
Results: After Shi Xiao San treatment, the growth of ectopic tissue in rats with endometriosis was significantly suppressed, their thermal radiation pain and mechanical pain thresholds increased, the density of nerve fibres and the expression of inflammatory factors in ectopic tissues reduced, and inflammatory cells infiltration in the dorsal root ganglion of the animals alleviated. Meanwhile, the expression of TRPV1 in the dorsal root ganglion was downregulated in rats with endometriosis.
Conclusions: Shi Xiao San could possibly inhibit the development of endometriosis and relieve pain in patients with endometriosis by reducing inflammatory responses in ectopic tissue and the dorsal root ganglion.