Zhen Ci Yan Jiu. 1990 ; 15(2): 130-5.

[The effect of extradural injection of capsaicin on pain threshold and electroacupuncture analgesia of rat]

Zhang Y, Zhang Z, Liang X, Guan X, Ai M.

Research Department of Acupuncture Analgesia Mechanism, Tongji Medical University.

The present paper is designed to investigate the variation of pain threshold and electroacupuncture analgesia of rat, and to observe the immunohistochemical changes in spinal ganglion and dorsal horn of lumber and sacral segment of spinal cord after extradural administration of capsaicin (100 micrograms/rat). It was found: 1. Obvious decrease of pain threshold 60 mins after injection of capsaicin, and the pain threshold restored nearly to the level of pre-treatment at 90 mins of post-treatment of capsaicin. 2. Apparent elevation of pain threshold on 1st-15th day after injection of capsaicin. 3. The efficiency of electroacupuncture analgesia 7th day after injection of capsaicin was obviously weaker than that of pre-treatment of drug and that of solvents treatment in the animals of control group. 4. The SP-LI, ENK-LI and FRAP were all weakened in dorsal horn of spinal cord 1h after capsaicin treatment. However, on the 7th day, with the exception of decrease of SP-LI and FRAP, the ENK-LI in dorsal horn was strengthened and the activity of FRAP in spinal ganglionic cells of B type disappeared. The foregoing results indicated that the metabolism and function of C fibers of primary afferent especially the SP containing nerve and those of ENK-containing neurons could be influenced by the extradural injection of capsaicin. And the primary afferent C fiber (including the SP containing nerve) may play important roles in the input of the informations of pain, and needling, as well as in the acupuncture analgesia.