Preliminary Observations Of The Effect Of Acupuncture On The Direct Cortical Responses (Dcr) In Cat

Yang Boyi, Jiang Deming, Wang Jing (Department of Biology, Fudan University)

In the research work on the mechanism of acupuncture analgesia, cortical evoked potentials are widely used to study the effects of acupuncture on the functional  state of the cerebral cortex. However, the results obtained from such investigation can only be regarded as the consequence of interaction of acupuncture and peripheral afferent signals in various levels of CNS. Herewith, we are seeking for some evidences to show how the cerebral cortex itself be influenced directly by acupuncture.

The direct cortical responses (DCR) are potentials recorded from cortical surface nearby the stimulating electrode. While current is delivered to the cortical surface, a multi-phases wave can be led from the adjacent area. It has been suggested that the negative and positive components of DCR separately represent the activities of apical dendrite and cell body of cortical neuron.

In the paper reported here, the DCR were employed for studying the effects of acupuncture on the electrical activity of the cerebral cortex. 20 adult cats were used in this acute studies. The animals were paralyzed with flaxedil intravenously, and the preparations were subsequently maintained on artificial respiration. The cortex was exposed unilaterally. Both the recording and stimulating electrodes were placed on the cortical surface of secondary somatosensory area (SII). The negative wave of DCR elicited by square pulse 0.1~0.4 mA) were recorded at intervals of 10 minutes. The waveform and amplitude of DCR were maintained stably in one hour. After needling the contralateral points "Neikuan" "Heku", the amplitude of DCR began to reduce in 10 minutes, and after 30 minutes the inhibitory effects were more remarkable (P<0.01). Withdrawing the electrical needle, the negative wave DCR recovered gradually in 20-30 minutes. The experiment of administration of pentobarbitone showed that after injection of pentobarbitone sodium the effects of acupuncture on DCR did not appear.

The results indicate that the acupuncture can depress the DCR recorded from SII in cat. So it may be considered that the acupuncture exerts an inhibitory effect on the functional activity of the cerebral cortex probably through the reticular formation of the brain stem.