Acupuncture Analgesia

Acupuncture is a unique therapy because it uses fine needles to inoculate minute intrusive traumas or lesions into the tissue, which stimulates many of the survival mechanisms of the body. Acupuncture needling and the induced lesion activate self-healing mechanisms, including restoring homeostasis, facilitating repair mechanisms such as anti-inflammatory reaction and tissue regeneration and pain modulation, after removal of the needles, the needle induced lesion continue to stimulate the body. There are four defensive physiological system, they include: 1- nervous system which coordinates our responses to external and internal condition. 2- Cardiovascular system which function as a highway to transport and provide energy, active molecules, and cellular cleansing. 3- Endocrine system, which secrets molecules for different conditions. 4- Immune system, which defends the body from invaders. (Ma et al; 2005)
There are four ways that acupuncture heals body:
1- Stress relief: needling reduces body stress by stimulating the secretion of endorphins, relaxing the cardiovascular and muscular system, restoring homeostasis.
2- Activation and control of immune and anti-inflammatory mechanism: needling and needle induced lesions are foreign invaders to our body. Acupuncture caused lesion cause an increase in the number and activity of immune cells and control inflammatory process via BS-HPA axis which in turn reduces both acute and chronic inflammation.
3- Acceleration of tissue healing: soft tissue such as nerves, muscles, connective tissues such as tendons, ligaments, joint capsule, and fascia, and some functional structures like blood and lymphatic vessels. Acupuncture also can reduce the inflammation of these soft tissues which can be caused by internal problems.
4- Pain relief: Acupuncture can cause pain relief by achieving endorphin release and other chemicals. ( Ma et al; 2005)
The mechanism of pain relief in acupuncture is a complicated process. Needling stimulates the following skin tissue. (Ma et al; 2005)
1-Afferent somatic neuron fibers such as cutaneous A-delta and C fibers which transmit the message from cutenous region to spinal cord, and sympathetic neuron fibers which control sweat glands and fine blood vessels.
2- Fine arterial and venous blood vessels
3-Lymphatic tissue and mast cells
4- Connective tissue.
When acupoint transits from latent phase to passive phase, it becomes tender which cause an increase in skin electrical conductance and decrease resistance in the area around the acupoint. Inserting a needle into this acupoint will cause an acute inflammatory response; the first response is the flare response resulting in redness of the skin around the needle. This vasodilatation function is via ANS (autonomic nervous system) which is mediated by substance P secreted from cutaneous nociceptive sensory nerves. The immune reaction is activated by mast cells which produce histamine, platelet activating factor and leukotrienes. (Ma et al; 2005)
Human body surface has an electrical energy since it is affected by electro-magnetic field of the earth. Dry skin has a DC resistance of 200,000 to two million ohms, at acupuncture points this resistance is down to 50,000 ohms; in patient with chronic pain, there is no difference in conductance between acupuncture points and nearby control points. In a chronically sick person, the acupoints transit from healthy tissue to tender or sensitized tissue, the sensitive area of the acupoints get lager which contributes to high electrical conductance and low resistance. Insertion of a metal needle makes a short circuit from the skin battery and creates a microcurrent called current of injury moving from inside to outside. The tiny lesion created by acupuncture needle causes negative charge at needling site and produces 10mA of current of injury which benefits growth and regeneration. (Ma et al; 2005)
These microcurrents created by needling are not sufficient to generate never pulses to spinal cord; therefore, repeated needling will not cause a “needling tolerance”. It has been suggested that electro-acupuncture is more effective in relieving pain, and it depends on the level of frequency of stimulation. Studies have shown 4 Hz releases enkephalin and beta-endorphin, and high frequency stimulation at 100Hz releases serotonin and norepinephrine. (Rapson et al; 2008)
The main focus of an acupuncturist during needling is to get the sensation of de qi, which is achieved by specific manipulation of the needles to increase the effectiveness of muscle relaxation and pain relief. When a needle is inserted into body tissue, there is an initial coupling between the metal needle shaft and elastic and collagen fibers, which is caused by both surface tension and electrical attraction between metal needle and electrical tissue charges (Ma et al; 20005). The rotation of needle increases the tension of the fibers by winding them around the needle, which pulls and realigns the connective tissue fiber network (Ma et al; 2005). In response to this mechanical deformation, there are cascade of cellular and mechanical events generated by the cells which include the following:
1-intracellular cytoskeletal reorganization
2-cell contraction and migration
3- Autocrine release of growth factors, and activation of intracellular signaling pathways and of nuclear binding proteins that promote the transcription of specific gene
all the above effects can lead to synthesis and local release of growth factors, cytokines, vasoactive substances, degradative enzymes, and structural matrix elements which in turn promote local healing (Ma et al; 2005)

Refrences:

Ma Y.T, Ma M, Cho Z.H. Biomedical Acupuncture for pain management. Elsevier, 2005. Chapter 3&4.