Objective: To investigate the relationship between mast cell degranulation and acupuncture analgesia.
Methods: A total of 58 SD male rats were randomly divided into control (n = 12), model (n = 12), needle-retaining (n = 12), electroacupuncture (EA, n = 12) and manual-acupuncture (MA, n = 10) groups. Arthritis model was established by injection of complete Freund's adjuvant (0.05 mL) into the left ankle-joint. The paw withdrawal latency (PWL) was detected with a radiant heat algesimeter. Electroacupuncture (EA, 2/100 Hz, 0.5-1.5 mA) or manual acupuncture (lifting and thrusting force being 240-280 mN, torque being 10-15 mN x mm, 3 times/s) were applied to "Zusanli" (ST 36) on the affected side for 30 min in the corresponding group. After decapitation (under anesthesia), skin tissue around the stimulated ST36 was sampled, cut into sections (5 microm), and stained with Toluidine Blue for observing the count of degranulated mast cells.
Results: In comparison with control group, PWL values of model, needle-retaining, EA and MA groups decreased significantly after modeling (P < 0.01); while compared with needle-retaining group, PWL values of EA and MA group increased considerably (P < 0.01), suggesting production of analgesia. After EA and MA stimulation, degranulation of mast cells in the stimulated ST36 area appeared apparently. Compared with needle-retaining group, the degranulation ratios of mast cells in EA and MA groups were obviously higher (P < 0.01).
Conclusion: Both EA and MA stimulation of "Zusanli" (ST 36) can effectively raise pain threshold, simultaneously, and enhance the degranulation ratio of mast cells in the stimulated ST36 area.