Therapeutic Mechanisms of Acupuncture

An explosion of acupuncture research beginning in the 1980s has produced sufficient basic studies such that synthetic models of acupuncture's therapeutic mechanisms are now available. A comprehensive synthesis that describes the neural, vascular, immunological, and endocrine responses to acupuncture may be found in Dr. Donald E. Kendall's recent peer-reviewed publication The Dao of Chinese Medicine: Understanding an Ancient Healing Art (Kendall 2002). The following excerpt is from Dr. Kendall's summary of acupuncture mechanisms (emphasis added):

Inserting a needle provokes and acute local defensive inflammatory response [that] provokes afferent nociceptive (pain) neurons that distribute to the dorsal horn of the spinal cord (1). These pain neuron signals then trigger gamma loop efferents in the ventral horn (4), and also activate neurons that cross over to the other side of the spinal cord to be transmitted up to the brain (3). Some of this information (3) travels to the sensory cortex, when the individual may consciously experience needling sensations. Most of the data travels to the brain stem regions.

Activation of the afferent muscle spindle static load proprioceptive neurons (2), either by the gamma loop (via 4 and 5), or possibly by bradykinin (B2) released during needling, transmits signals to the spinal cord dorsal horn. Both nociceptive and proprioceptive signals stimulate additional neurons that transmit signals to the ventral horn of the spinal cord (4), which activate somatic motor nerves (5) to muscles, and autonomic motor nerves to peripheral blood vessels (6) and to the internal organs (7).

Afferent proprioceptive information is also transmitted up and down the spinal cord producing muscle, nociceptive, and visceral reflexes along the cord remote from the spinal segmental level at which the stimulation is provided. The neurons associated with the muscle system comprise a pathway known as the gamma loop (2, 4, and 5), which is necessary for muscle function even though voluntary motor signals are provided by descending response pathways (8) from the brain. Afferent muscle information is also transmitted to the brain via ascending pathways (3) in spinal tracts different from those carrying the pain signals. Certain regions or nuclei within the brain stem, involving the periaqueductal gray and several raphe nuclei, including the nucleus raphe magnus, eventually activate supraspinal descending pathways in the spinal cord (9), which provide inhibition and control. These signals can inhibit pain, relieve muscle contractions, normalize vascular tone, and restore blood flow. Inhibition of autonomimotor fibers also normalizes organ activity. Descending control is only directed back down to spinal segmental levels that are stimulated by needling (Foreman, Hammond, and Willis: 1981; Foreman: 1986). "Internal organs, including blood vessels, also have afferent nociceptive neurons (10) that indicate pain and inflammation.

These signals also transmit to the dorsal horn of the spinal cord…. If the pain signals from the viscera (10) exceed a certain threshold, then the neurons in the somatic nociceptive pathway (1) can be activated antidromically to produce referred pain in the related somatic receptive field…Afferent nociceptive visceral neurons (10) can also stimulate muscle reflexes (involving 4, 5, and 10).”

(Kendall, 2002)

Other peer-reviewed models of acupuncture mechanisms include Dr. Charles Shang's “Electrophysiology of Growth Control” model, and Dr. Helene Langevin's connective tissue winding model. Shang describes the nodal and vessel system as sharing significant electro-physiological characteristics with the morphogenetic fields and growth control system that guide cell and tissue development, architecture, and specialization from the embryo through adulthood. The acupuncture nodes and vessels represent points and pathways of maximal bioelectric signal transmission and transduction, and are both reflective of pathogenesis, and sensitive to non-specific stimuli. Stimulation of acupuncture nodes and vessles may have wide-ranging and profound effects through the regulation of all body systems via the electrophysiological growth control system.

Studies conducted by Dr. Langevin et. al. suggests that mechanical coupling between the needle shaft and elastin and collagen fibers in subcutaneous connective tissue occurs as the practitioner rotates the needle in classically-prescribed manipulations. Rapid increase in needle-tissue torque facilitates the generation and propagation of electro-chemical signals through connective tissue planes. Studies of tissue samples following needle manipulation suggest that changes in tissue architecture persist after needle withdrawal. The downstream effects of connective tissue winding may include altered gene expression, protein synthesis, and secretion of autocrine and paracrine factors.

While emphasizing different dimensions of acupuncture therapeutic mechanisms, these models are not inconsistent with the neurovascular models developed by researchers such as Dr. Kendall. The time may be near when various models of acupuncture mechanisms may be synthesized into a comprehensive theory that unites well-known physiological mechanisms with scientific explanations of the subtler aspects of acupuncture effects that have often been described as “energetic.”

Copyright Essential Health Care Network 2003

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