P物质是伤害性刺激一级传入的神经递质。我组以前的实验证明

电针镇痛的大鼠低位脑干与腰髓的P物质含量增加。当大鼠脑池注射5.7-双羟色胺一周后再给电针

电针镇痛作用被去除

此时脑干和P-Chlorophenylalanine (PCPA) 250mg/kg IP. was given to a group of rats. 72 hrs later the electro-acupuncture analgesia was tested and substance P (SP) in the brain stem and the lumbar spinal of the rats was determined by RIA. After PCPA injecting the electro-acupuncture no longer caused analgesia but lowered the pain threshold. Meanwhile the level of SP in the brain stem and lumbar spinal did not inereased but much lowerd than the group of vihicle injection combined with electro-acupuncture. It suggests that by PCPA depleting the 5-HT in CNS and abating the 5-HT-energic descending inhibition the electroacupuncture no longer causes analgesia but promotes the SP transmitted release. It further suggests that in lower brain stem and spinal transmission of SP was regulated by descending inhibition. Analgesia of electro-acupuncture activates the 5-HT-energic descending inhibition and decreases the nociceptive transmission of SP partly.