Characteristics of afferent fiber innervation on acupuncture points zusanli.

Acupoint zusanli is one of the most effective points in traditional Chinese medicine. Needling point zusanli has a significant suppressive effect on jaw movement response (JMR) and electromyogram of digastric muscle (dEMG) induced by peroneal nerve stimulation. This effect is weakened or abolished by sectioning the peroneal nerve and blocking A-beta- and some A-delta-fibers in the nerve. When the point zusanli is stimulated electrically a larger-than-normal proportion of A-beta-fibers is activated. Local afferent fiber composition at this point contains more myelinated fibers, more large-sized fibers, and more A-beta-fibers than nonacupoints. This predominance of large afferent fibers in the composition and activity of point zusanli is thought to be one of the fundamental characteristics of the point in regard to its structure and function and contributes to its powerful acupuncture effect.