以往

我们曾观察到吗啡拮抗剂纳洛酮能大部分阻断针刺抑制内脏痛的反应

说明针刺镇痛过程的实现有内源性吗啡样物质的参与。据报导

电刺激大鼠、兔、猫、猴和人体的中脑导水管周围灰质[Mesencephalic pe-Experiments were performed on 59 rats slightly anesthetized with urethane. The activities of 161 units localized in PAG were extracellularly recorded with a glass microelectrode. The splanchnic nerve or tail was stimulated by a brief train of 10-20 rectangular pulses ( duration 0.5-1.0 ms

interval 10 ms

intensity 10-20 V or 2-4 mA) which was used as noxious stimulation. Electro-acupunture was applied to "Zusanli" or "Beishu" points. It was found that the majority of units(about 80O%) responded with increased frequency

about 6% showed decreased frequency and the remainder had no response to nociceptive stimulation(applied to the splanchnic nerve and tail.) It seems to imply that PAG is one of the brain structures which receive somatico-visceral pain impulses. The inputs originated from different stimulating sites of the body and electro-acupuncture points could converge on the same unit and interact in PAG. The effect of electro-acupuncture resembles that of morphine which inhibits nociceptive neuronal discharges in PAG. It shows that PAG is closely related to acupuncture analgesia These results suggest that the integration in paramedianascending system including PAG

and activation of descending inhibitory system down to spinal cord might be considered as two main functional patterns of the inhibition of somatico-visceral pain by electro-acupuncture.