Objective : Zusanli(ST36) and Hoku(Li4) are analgesic acupuncture points frequently used for acupuncture in Oriental medicine. The present study was conducted to see the antinociceptive effects produced by electroacupuncture combined two frequencies(Low, High) and two different acupuncture points(LI4, ST36) in the rat tail flick test.
Method : In this study the Rats (Sprague-Dawley, 250-300g) were partially anesthetized with thiopental sodium(40㎎/㎏, i.p.). The basal reaction time for the tail-flick was 3±0.5 sec. Low frequency(3㎐, 5V, biphasic) and high frequency(100㎐, 5V, biphasic) were applied to the inserted needle for the period of insertion(twenty minutes). Experimental groups are divied as follow; a) electroacupuncture stimulation groups at Hoku with or high frequency(L-EA, H-EA), b) electroacupuncture stimulation groups at Zusanli with low or high frequency(1-EA, h-EA), c) low frequency at Hoku and Zusanli(LIEA), d) low frequency at Hoku and high frequency at Zusanli(LhEA), e) high frequency at Hoku and low frequency at Zusanli(HIEA), f) high frequency at Hoku and Zusanli(HhEA)
Results : The individual stimulation at either Hoku or Zusanli with low frequency has stronger and longer analgesic effect than high frequency stimulation. In addition, the combined stimulation at Hoku and Zusanli with low frequency has superior effect to individual stimulation with low frequency. LhEA and LIEA have superior effect to other stimulation groups among the combined groups.
In order to determine the involvement of opioid system on the different antinociceptive effects, Naloxone, an opioid antagonist, was used in the combined groups. LIEA is the most sensitive when naloxone was administrated among study groups. HhEA is the least sensitive in the administration of naloxone.
Conclusion : From results, this study confirmed that the opioid system is involved in analgesic effect of low frequency stimulation of acupuncture point, and we also can suggest the stronger analgesic effect of combining stimulation points is due to the theory of spatial summation in the nervous system.
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