[Influence of 5.7-dihydroxytryptamine on electro-acupuncture analgesia and substance P level in central nervous system of the arthralgic rats].

The relation between electroacupuncture (EA) analgesia (A) and substance P (SP) level in the brain stem (BS) and lumbar spinal cord (LSC) of arthralgic rats was investigated. The rats were divided into three groups: 1)5.7-dihydroxytryptamine (5.7-DHT) + EA, 2) vehicle (V) + EA, and 3)5.7-DHT. All the animals were induced arthralgesia by injecting Freund's adjuvant 7 days after cisterna injection of 5.7-DHT or vehicle. The SP level in the BS and LSC was determined by RIA. The results indicated that in V + EA group the EA could prolong tail flick latency by 39.6%, but in other two groups did not. The SP level in LSC of V + EA group (179.1 +/- 11.5 pmol/g) was higher than that in the 5.7-DHT + EA (135.9 +/- 9.3pmol/g) and 5.7-DHT (125.8 +/- 10.0 pmol/g) groups. It suggested that both EA and arthralgia could activate the descending 5-HTergic inhibitory system to inhibit the release of SP in LSC. When the 5-HTergic system was destroyed by 5.7-DHT, the EAA was attenuated, and the SP level in LSC was lowered due to its release was decreased by EA and arthralgia.