A Role of Substancy P Containing Primary Afferent Fibers for The Electro-acupuncture Analgesia / 全日本鍼灸学会雑誌

ABSTRACT

The effects of local application of capsaicin (CAP) to peripheral nerves on electroacupuncture (EA) analgesia were behaviorally examined in the rats. Pain threshold, datermined by using a hot-plate and tail-flick methods, increased to 160-180% of the control value after EA, which was applied to the acupuncture points between LI-11 and LI-12 of the rat forepaw. After the local application of CAP to the radial, ulner and median nerves of the animal's right forepaw, the EA, applied to the treated forepaw, did not significantly change the pain threshold. In the same animals, the EA applied to the untreated side increased the threshold as high as that before the CAP treatment. This indecates that the EA became ineffective on the CAP treated side, this ineffectiveness of the EA cont inued until at last 15 days in the case of the single CAP treatment for 15min, on the peripheral nerves. The substance P (SP) concentration in the spinal dolsal horn (C5-7) of these animals, which was measured by radioimmunoassay, was about 40% lower in the CAP treated side than in the untreated side.<br>These results suggest that SP-containing primary afferents, of which nerve conduction was probably blocked by treatment whth CAP, convey information for EA analgesia.