Analgesic effect of different moxibustion durations in rheumatoid arthritis rats

OBJECTIVE: To observe the influence of different moxibustion durations on hypothalamic pro-opiomelanocortin (POMC) and prodynorphin (PDYN) mRNA expressions and plasma beta-endorphin (beta-EP) content in rheumatoid arthritis (RA) rats, to understand the mechanism of moxibustion analgesia and its dose-effect relationship. METHODS: Twelve male Wistar rats were randomly selected from 48 male Wistar rats as a normal control group. The RA model was created by raising rats in a windy (blowing with electric fan), cold (6 degrees C +/- 2 degrees C), and wet (80%-90% humidity) environment for 20 days, 12 h each day. This was followed by injection of Freund's complete adjuvant (0.15 mL) into the ankle. Then, rats were randomly divided into a model group, moxibustion group I, and moxibustion group II, with 12 rats in each group. In moxibustion groups I and II, moxibustion was given at Shenshu (BL 23) and Zusanli (ST 36) for 20 and 40 min, respectively, once daily for 15 days. Hypothalamic POMC and PDYN mRNA expression levels and plasma beta-EP content were determined. RESULTS: Compared with the normal group, the pressure pain threshold decreased, while the hypothalamic POMC and PDYN mRNA expression levels and plasma beta-EP content increased in the moxibustion groups (P < 0.01). Compared with the model group, the pressure pain threshold, hypothalamic POMC and PDYN mRNA expression levels and plasma beta-EP content in the moxibustion groups increased significantly (P < 0.01). Compared the moxibustion group I, the pain threshold, hypothalamic POMC and PDYN mRNA expression levels and plasma beta-EP content in moxibustion group II significantly increased (P < 0.01). CONCLUSION: Moxibustion has an analgesic effect and increases hypothalamic POMC and PDYN mRNA expression levels and plasma beta-EP content in RA rats.The analgesic effect in moxibustion group II is betterthan that in moxibustion group I.