The Effect Of Electro-Acupuncture On The Cortical Evoked Potential Caused By Nociceptive Stimulus Upon Lower Abdominal Skin

Zhou Jiayin, Li Xuebing, Gu Zengfa, Yang Langming (Department of Physiology, Lanzhou Medical College)

The cortical evoked potential (EP) caused by nociceptive stimulus upon lower abdominal skin was taken as an index to clarify the possibility of a  relative specific connection between the central projections of electro-acupuncture point and the operative incision site, and for finding of more effective point and appropriate parameter for electro-acupuncture. The results of 25 rabbits were as follows:

1. Electro-acupuncture frequency 15 Hz upon Lumbar 1 (a new point) or Ciliao, showed a marked depressive effect on EP; whereas the effect of Zusanli and Sanyinjiao were moderate; and there was no effect with Quchi and Sibai. The results showed that the effect of points on EP had a relative specificity spatially. The mechanism might be concerned with segment innervation of the nervous system.

2. When electro-acupuncture stimulation with frequency of 5, 15, 40 and 80 Hz, but of the same intensity were used to stimulate the Ciliao point, the effects of 5 and 15 Hz showed marked depressive effect on EP; that of 40 Hz was weaker and 80 Hz with no effect.

3. If a single shock was delivered to Ciliao point and then a nociceptive stimulus was given to the skin of lower abdomen at 50 or 100 milliseconds interval, the EP was markedly depressed. When the interval of these two stimuli increased to 200, 300 or 400 milliseconds respectively, no effects on EP was elicited. The above results demonstrated that the decreased effect is the result of the interaction in CNS between the afferent information of Ciliao point and that of the skin of lower abdomen caused by nociceptive stimulus applied within certain intervals.

4. If the electro-acupuncture at Lumbar 1 or Ciliao lasted 20 minutes, the EP caused by nociceptive stimulus to the skin of lower abdomen was supressed persistently during the acupuncture period. After the cessation of the stimulation, EP recovered rapidly to the normal level.

From the above results, it seemed reasonable to suppose that there may be a relatived specific connection between the central projections of the acupuncture point and the operative incision site. Therefore, we can consider to select a more suitable point according to the principle of segment innervation and a more effective electro-acupuncture parameter to acquire better analgesic effect.