Shen E (Shanghai Institute of Physiology, Academia Sinica)
It was first demonstrated by Hu et al that electrical stimulation of the spinal cord of rabbit caused analgesia which was mediated by a descending inhibitory system. Afterward we observed that descending inhibition was also involved in the inhibitory effect of acupuncture on the viscerosomatic reflex in the cat. After high spinal transection the inhibitory effect caused by electric needling the points on the lower limb was almost abolished. The descending spinal pathway was located in the dorsolateral funiculi near the dorsal horns. The ventrolateral funiculi seemed to be the ascending pathway of acupuncture signals. After section of the ventrolateral funiculi at T2-3, the inhibitory effect of hindlimb electro-acupuncture disappeared, but the effect of needling the points on the forelimb still persisted. It was evident that activation of some supraspinal structures by the acupuncture signals by way of the ventrolateral funiculi was necessary for the inhibitory effect.
Various transections and lesions placed in the brain showed that the descending inhibitory influence mainly originated from the bulbar medial reticular formation including the nucleus raphe magnus. Injection of 5,6-dihydroxy-tryptamine into the lateral ventricle or the nucleus raphe magnus diminished the acupuncture effect significantly.
Section of the dorsolateral funiculi or a lesion placed in the bulbar medial reticular formation diminishe dthe inhibitory effect of electro-acupuncture on the splanchnically evoked potentials in the orbital cortex. Since the evoked potential did not appear until the A-delta fibers in the splanchnic nerve were excited, it was concluded that the asecending transmission of the visceral A-delta impulses could be partially blocked by descending inhibitory impulses induced by elctro-acupuncture.
On the basis of above experiments, we could see a spino-bulbospinal recurrent circuit underlying the inhibitory effect of acupuncture. Stimulation of any part of this circuit could evoke a dorsal root potential (DRP) at the thoracic (T[11]) or lumbar (L6-7) level. Correlation was observed between temporal course of the DRP and that of the inhibitory phase of the viscerosomatic or flexor reflex conditioned by the same stimulus which evoked the DRP. The length constant of the afferent fibres involved in the dorsal root potential was about 3mm, suggesting depolarization of fine myelinated fibres. Presynaptic inhibition was thus suggested to be an important component in the descending inhibitory effect induced by acupuncture.
It was first demonstrated by Hu et al that electrical stimulation of the spinal cord of rabbit caused analgesia which was mediated by a descending inhibitory system. Afterward we observed that descending inhibition was also involved in the inhibitory effect of acupuncture on the viscerosomatic reflex in the cat. After high spinal transection the inhibitory effect caused by electric needling the points on the lower limb was almost abolished. The descending spinal pathway was located in the dorsolateral funiculi near the dorsal horns. The ventrolateral funiculi seemed to be the ascending pathway of acupuncture signals. After section of the ventrolateral funiculi at T2-3, the inhibitory effect of hindlimb electro-acupuncture disappeared, but the effect of needling the points on the forelimb still persisted. It was evident that activation of some supraspinal structures by the acupuncture signals by way of the ventrolateral funiculi was necessary for the inhibitory effect.
Various transections and lesions placed in the brain showed that the descending inhibitory influence mainly originated from the bulbar medial reticular formation including the nucleus raphe magnus. Injection of 5,6-dihydroxy-tryptamine into the lateral ventricle or the nucleus raphe magnus diminished the acupuncture effect significantly.
Section of the dorsolateral funiculi or a lesion placed in the bulbar medial reticular formation diminishe dthe inhibitory effect of electro-acupuncture on the splanchnically evoked potentials in the orbital cortex. Since the evoked potential did not appear until the A-delta fibers in the splanchnic nerve were excited, it was concluded that the asecending transmission of the visceral A-delta impulses could be partially blocked by descending inhibitory impulses induced by elctro-acupuncture.
On the basis of above experiments, we could see a spino-bulbospinal recurrent circuit underlying the inhibitory effect of acupuncture. Stimulation of any part of this circuit could evoke a dorsal root potential (DRP) at the thoracic (T[11]) or lumbar (L6-7) level. Correlation was observed between temporal course of the DRP and that of the inhibitory phase of the viscerosomatic or flexor reflex conditioned by the same stimulus which evoked the DRP. The length constant of the afferent fibres involved in the dorsal root potential was about 3mm, suggesting depolarization of fine myelinated fibres. Presynaptic inhibition was thus suggested to be an important component in the descending inhibitory effect induced by acupuncture.
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