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Acupuncture: Difference between revisions
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== Effectiveness == | == Effectiveness == | ||
Gate-control theory of pain | |||
The "gate control theory of pain" (developed by Ronald Melzack and Patrick Wall in 1962[54] and in 1965[55]) proposed that pain perception is not simply a direct result of activating pain fibers, but modulated by interplay between excitation and inhibition of the pain pathways. According to the theory, the "gating of pain" is controlled by the inhibitory action on the pain pathways. That is, the perception of pain can be altered (gated on or off) by a number of means physiologically, psychologically and pharmacologically. The gate-control theory was developed in neuroscience independent of acupuncture, which later was proposed as a mechanism to account for the hypothesized analgesic action of acupuncture in the brainstem reticular formation by a German neuroscientist in 1976.[56] | |||
This leads to the theory of central control of pain gating, i.e., pain blockade at the brain (i.e., central to the brain rather than at the spinal cord or periphery) via the release of endogenous opioid (natural pain killers in the brain) neurohormones, such as endorphins and enkephalins (naturally occurring morphines). | |||
[edit] Neurohormonal theory | |||
Modern acupuncture model. | |||
Pain transmission can also be modulated at many other levels in the brain along the pain pathways, including the periaqueductal gray, thalamus, and the feedback pathways from the cerebral cortex back to the thalamus. Pain blockade at these brain locations is often mediated by neurohormones, especially those that bind to the opioid receptors (pain-blockade site). | |||
Some studies suggest that the analgesic (pain-killing) action of acupuncture is associated with the release of natural endorphins in the brain. This effect can be inferred by blocking the action of endorphins (or morphine) using a drug called naloxone. When naloxone is administered to the patient, the analgesic effects of morphine can be reversed, causing the patient to feel pain again. When naloxone is administered to an acupunctured patient, the analgesic effect of acupuncture can also be reversed, causing the patient to report an increased level of pain.[57][58][59][60] It should be noted, however, that studies using similar procedures, including the administration of naloxone, have suggested a role of endogenous opioids in the placebo response, demonstrating that this response is not unique to acupuncture.[61] | |||
One study performed on monkeys by recording the neural activity directly in the thalamus of the brain indicated that acupuncture's analgesic effect lasted more than an hour.[62] Furthermore, there is a large overlap between the nervous system and acupuncture trigger points (points of maximum tenderness) in myofascial pain syndrome.[63] | |||
Evidence suggests that the sites of action of analgesia associated with acupuncture include the thalamus using fMRI (functional magnetic resonance imaging)[64] and PET (positron emission tomography)[65] brain imaging techniques,[66] and via the feedback pathway from the cerebral cortex using electrophysiological recording of the nerve impulses of neurons directly in the cortex, which shows inhibitory action when acupuncture stimulus is applied.[67] Similar effects have been observed in association with the placebo response. One study using fMRI found that placebo analgesia was associated with decreased activity in the thalamus, insula and anterior cingulate cortex.[68] | |||
Recently, acupuncture has been shown to increase the nitric oxide levels in treated regions, resulting in increased local blood circulation.[69][70] Effects on local inflammation and ischemia have also been reported.[71][http://en.wikipedia.org/wiki/Acupuncture] | |||
== References == | == References == | ||
*[http://en.wikipedia.org/wiki/Acupuncture Acupuncture] by several authors. Wikipedia, the free encyclopedia. | *[http://en.wikipedia.org/wiki/Acupuncture Acupuncture] by several authors. Wikipedia, the free encyclopedia. | ||
