Objective: To probe the physiological mechanism of propagation of needle feeling along the meridian pathway during acupuncture.

Methods: Neuro-physiology and histo-chemistry were used in these studies for recording reflexive activity of acupuncture points and observing nervous projections innervating muscular acupuncture points in the given meridian at the spinal cord.

Results: Some findings have been obtained from the studies on the innervation of acupuncture points and the reflexive characters: (1) There is a strong evidence that muscular compartments correspond closely to acupuncture points. The central branches of sensory fibers supplying muscular compartments project to dorsal gray of spinal cord in well-oriented arrangement, for example, the afferent fibers innervating upper compartment of the anterior tibial muscle (Point Zusanli) occupy the first two dorsal rootlats, the fibers from the middle compartments of the muscle (near the points Shangjuxu and Xiajuxu) entrance into the spinal via the third and fourth rootlets and the fibers of the lower ones (point Fenglong) take the fifth rootlet A similar result to those of the afferent projection of the muscle was obtained from their reflexive outputs recorded from the nerve filament supplying the different compartments, stimulation of the first nerve branch innervating point Zusanli evoked outputs with 25- 40 uV in amplitude and as short as 10 ms of latency at the second and third nerve branches, however, output with 20-30 uV amplitude and 13 ms latency could be recorded from the fourth and fifth nerve branches only by stronger stimulation showing a graded decrease of the output amplitudes was followed by increase of the distance between stimulating and recording points. A similar experiment in decerebrate cats using natural stimulation supports also the above mentioned results, We found that a recruitment effect of the muscle motoneuron pool elicited by local mechanical stimulation or acupuncture--like stimuli can spread to the other motoneuron pool supplying the adjacent and distal compartments and evoked a reflective activity in these muscle compartments, like those thought similar to that of needle feeling along the meridian pathway during stimulation of acupuncture points; (2) The well-oriented arrangement of afferent and efferent nerves of the muscle compartments is closely parallel to the architecture of motoneurons supplying acupuncture points in the ventral horn. A technique of retrograde labeling of the motoneuron with CH-HRP was used to probe the location of the labeled motoneurons supplying acupuncture points or muscle compartments. We found that each acupuncture point is supplied by small group of motoneuron, these neuron groups of homomeridian acupuncture points form a discrete longitudinal column. The column is the mirror image of the acupuncture points of a given meridian pathway and there are dentro-dentritic projections occuring in the labeled motoneurons; (3) Rest membrane potential of the motoneuron was recorded as a index to evaluate their physiological function of the dentro-dentritic projections. A depolarizing shift of the motoneuron could be elicited.

By Xie Yikuan, Zhou Huihui, Ma Cao & Chao Huhen.