[The influence of P-chlorophenylalanine on the analgesia of electro-acupuncture and the level of SP in CNS of rats].

P-Chlorophenylalanine (PCPA) 250 mg/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 increased but much lowered than the group of vehicle 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 electro-acupuncture 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.