Mechanistic Basis of Acupuncture - Article Example

Mechanistic Basis of Acupuncture Introduction Acupuncture is one of the oldest, most commonly used medical procedures in the world which originated in China more than 2,000 years ago. The practice of acupuncture includes procedures involving stimulation of anatomical points on the body by a variety of techniques. American practices of acupuncture incorporate medical traditions from China, Japan, Korea, and other countries. The acupuncture technique that has been most studied scientifically involves penetrating the skin with thin, solid, metallic needles that are manipulated by the hands or by electrical stimulation. Acupuncture is effective for relieving dental pain, chronic pain, back pain, and headache. It reduces nausea and vomiting after surgery and chemotherapy. It also reduces nausea associated with pregnancy (Kaptchuk 374-383). It is not fully known as to what is the mechanism of action behind these effects. Various theories have been put forward by scientists. As early as 1974, a research group from Peking studied the mechanism on rabbits. They found that infusion of cerebrospinal fluid from a rabbit that had undergone acupuncture into a naive rabbit resulted in significant increase in the pain threshold of the recipient rabbit.  So the researchers thought that substances that are released from the central nervous system mediated acupuncture-induced analgesia.  Later, several researches pointed to the stimulation of secretion of endogenous morphine-like substances called endorphins (Kaptchuk 374-383). The studies proposed that these endorphins act on the opiate receptor sites and inhibit the transmission of pain signals. The evidence to support this action was that endorphin levels in blood and cerebrospinal fluid increased in response to acupuncture and naloxone and other opiate receptor antagonists blocked this effect. Also, loss of opiate receptors in genetically altered mice resulted in suppression of this effect. Some other studies have shown that acupuncture stimulates type 3 small afferent fibers within muscle tissue (Stux 187: 209). These fibers which are connected to the hypothalamus-pituitary axis act both locally through the spinal cord, and systemically through the release of neurochemicals. The local and distal pain suppressing effects of acupuncture is dependent upon electrical stimulation of the acupuncture needle. Different frequency and intensity of electrical stimulation determines whether the effect is local, i.e., within the region of the body innervated by a single spinal nerve tract or through the systemic secretion of neurochemicals. Recent data, obtained by using functional magnetic resonance imaging, suggest the ability of acupuncture to regulate more complex physiological processes and that acupuncture has regionally specific, quantifiable effects on relevant brain structures (Kaptchuk 374-383). Acupuncture may also stimulate gene expression of neuropeptides. Some of the recent theories have suggested connective tissue mediated mechanisms and electromagnetic mechanisms as mechanistic basis of acupuncture. Discussion Actually, acupuncture points and meridians are the core of traditional acupuncture practice, although anatomical and physiological explanations for these concepts remain elusive. The meridians connect the surface of the body to internal organs. In classic Chinese medicine theory, these meridians represent channels through which energy or "meridian qi" flows and involves electrical activity. It is because of this assumption that electrical point locators are commonly used in clinical practice and research. However, there is no experimental evidence in support of this practice. The associations between acupuncture points or meridians and certain electrical properties have remained controversial because most of the studies were actually limited by small sample sizes, poor research design, poor procedural descriptions, lack of rigorous statistical analyses and use of surface electrodes which were confounded by various factors including pressure, skin moisture, electrode contact and abrasion of the stratum corneum (Ahn 5-10). Langevin and Yandow in 2002 hypothesized that the network of acupuncture points and meridians can be viewed as a representation of the network formed by interstitial connective tissue. They supported this hypothesis by ultrasound images showing connective tissue cleavage planes at acupuncture points in normal human subjects. They mapped acupuncture points in serial gross anatomical sections through the human arm and found that there was 80% correspondence between the sites of acupuncture points and the location of intermuscular or intramuscular connective tissue planes in postmortem tissue sections. They proposed that the anatomical relationship of acupuncture points and meridians to connective tissue planes is relevant to acupuncture's mechanism of action and suggested a potentially important integrative role for interstitial connective tissue (Langevin and Yandow 257-265). In another study in 2002, Langevin and colleagues demonstrated that the thin acupuncture needles become coupled with connective tissue underlying the dermis. This mechanical event may then be transformed into a biochemical signal through a process called mechano-transduction. This mechanical signal is postulated to act both locally (near the site of needling) and at a distance via connective tissue planes (Langevin “connective tissue involvement” 872-874). Acupuncture needle manipulation gives rise to a bio-mechanical phenomenon which is characterized by an increase in the force necessary to pull the needle out of the tissue when compared to the force necessary to instill the needle. This is known as needle grasp. Langevin and colleagues investigated whether this needle grasp was due to winding of connective tissue or due to contraction of muscle. The principal findings in their investigations were: 1. Increased needle penetration of muscle does not result in greater pull out force than increased penetration of subcutaneous tissue. 2. Acupuncture needle rotation increases pullout force and subcutaneous tissue volume in the vicinity of the needle. 3. Acupuncture needle rotation results in deformation of subcutaneous tissue characterized by increase in periodic architectural order. These findings supported the fact that connective tissue winding is the mechanism responsible for increase in the pullout force induced by needle rotation and not muscle contraction. This study not only proved the involvement of subcutaneous tissue in needle grasp but also suggested that the mechanism of action of acupuncture also involves extra neural tissues. This defeated the idea of involvement of only neural or neuro-chemical mechanisms in the function of acupuncture. Thus, the results of this study highlighted the potential role of interstitial connective tissue in neuro-modulation. Acupuncture acts not simply via neural stimulation but also by producing changes in the connective tissue milieu surrounding sensory afferent nerve fibers. These connective tissue changes may be long lasting which may explain the claims that acupuncture can have prolonged therapeutic effects (Langevin “connective tissue involvement” 872-874). In a study by Ahn and others, they hypothesized that that segments of acupuncture meridians that are associated with loose connective tissue planes between the muscles or between the muscle and bone and which are visible by ultrasound have greater electrical conductance than non-meridian, parallel control segments. They combined ultrasound evaluation and tissue impedance measurements to examine the electrical properties of connective tissue planes associated with meridians Their results concluded that tissue impedance was lower along the pericardium meridian but not along the spleen meridian. The lack of difference at the spleen location might have been due to both control and meridian needles penetrating connective tissue and the tissue impedance might have been influenced by needle penetration of connective tissue, whether meridian-associated or not (Ahn 5-10). Several researchers have proposed that acupuncture may work via an electromagnetically based mechanism and that acupuncture points have increased conductivity and decreased resistance compared to surrounding skin. This implies that acupuncture points conduct electrical current better than elsewhere on the body. Reichmanis and others have proved that the electrical resistance of acupuncture points varies with disease states, sleep, urination, meals, birth and delivery, physical exercise, and changes in external environment such as temperature, time of day and season (Reichmanis 69-72). Acupuncture needles can create an electrical difference (voltage) between the end of the needle that is outside the body and the end inside the body by thermo-coupling, bimetallic effects and other methods. This voltage promotes the conduction of a current along the needle shaft and creates an electromagnetic field around the needle. The shaft of the needle remaining outside the body will receive and transmit electromagnetic signals from the environment. Bioelectromagnetics is now established as one of most visible and fruitful components of acupuncture therapy (Milburn 53-63). Endogenous electro-magnetic fields signal and regulate physiologic states, biologic and circadian rhythms, and immune and endocrine functions (Fedorowski 765-773). These fields have the distinguishing feature of being very low-level, low-frequency, and low-intensity, similar to those generated in the body by acupuncture and can stimulate and regulate physiological processes such as bone mending, cell division, and wound healing. Bioelectromagnetics research is divided into three areas: 1) basic mechanisms of electromagnetic-biochemical interaction; 2) systemic properties of electromagnetic regulation; 3) interaction between organism and (electromagnetic) environment. This field needs further studies and evidence. Conclusion The medical benefits of acupuncture are now well recognized by the Western medical community. A clear picture of the biological basis of acupuncture is only now emerging as a result of research in recent years. Actually, despite 20 years of research, the efficacy of acupuncture in general is not established. The term acupuncture is used to describe a variety of treatments that differ in many important aspects, both theoretical and technical and hence there is difficulty in drawing conclusion from existing literature (Langevin 167-75). There are many theories describing the mechanistics of acupuncture. The initial theories were in favour of release of endogenous opioids. Some others suggested stimulation of type 3 small afferent fibers within muscle tissue. However the connective tissues mediated mechanisms theory and electromagnetic mechanisms theory have emerged as the most successful theories of mechanistics of acupuncture. The connective tissues mediated mechanisms theory proposes that acupuncture mediates its effect through the connective tissue of the body whereas the electromagnetic theory proposes that acupuncture works via an electromagnetically based mechanism. References Ahn, Andrew, Wu, Junru, Badger, Gary, Hammerschlag, Richard and Langevin, Helene "Electrical impedence along connective tissue planes associated with acupuncture meridians." BMC Complementary and Alternative Medicine  (2005): 5-10. Fedorowski Artur, Steciwko Andrzej and Rabczynki Jerzy. "Influence of low-frequency electromagnetic field on growth of endogenous Morris hepatoma and its metastatic ability." Med Sci Monit 4. 5 (1998): 765-773. Kaptchuk, Ted. “Acupuncture: Theory, Efficacy, and Practice.” Annals of Internal medicine 136. 2 (March 2002): 374-383. Langevin Helene, Churchill David, Wu Junru. et. al " Evidence of connective tissue involvement in acupuncture." The FASEB Journal 16 (June 2002): 872-874. Langevin HM, Vaillancourt PD. "Acupuncture: does it work and, if so, how?" Seminar in  Clinical Neuropsychiatry 4. 3(July 1999):167-75. Langevin Helene and Yandow Jason. " Relationship of acupuncture points and meridians to connective tissue planes." The Anatomical record 269. 6 (Dec. 2002): 257-265. Milburn, MP." Emerging relationships between the paradigm of oriental medicine and acupuncture." American journal of acupuncture 23(1994):53-62. Peking Medical College, Research Group of Acupuncture Anaesthesia. “The role of some neurotransmitters of brain in finger acupuncture analgesia.” Scientia Sinica 17. 1 (1974): 112-130. Reichmanis M, Marino AA, Becker RO. “D.C. skin conductance variation at acupuncture loci.” American Journal of Chinese Medicine 4.1(1976):69-72. Stux, G and Hammerschlag, R. Clinical acupuncture: Scientific Basis Verlag: Springer, 2001. Read More