The meridian system and mechanism of acupuncture--a comparative review. Part 2: mechanism of acupuncture analgesia.

In traditional Chinese medicine (TCM), pain is never merely a sign of discomfort. It is usually an integral part of a particular disease or physiological malfunction. Thus pain should not be treated in isolation since it will disappear as soon as its cause is identified and removed. Hence, in this Part 2 of a three-part series, initially, clinical pathologies in modern medicine and TCM are compared. Then, the pain pathophysiologies of these two schools of thought are reviewed. In addition, certain unique features of acupuncture effects that any valid mechanism must account for are outlined. Finally, various mechanisms of acupuncture analgesia are reviewed. One plausible mechanism based on the meridian system of Part 1, i.e., the chaotic wave theory of fractal continuum in terms of the neurovascular network, is also proposed. It contends that the injury current due to acupuncture at an acupoint will trigger electromagnetic inductive effects so that the impedances of correlated neurovascular bundles are drastically changed. Two consequent scenarios are possible. (1) If the impedance of the meridian hugely mismatches with that of the brain after acupuncture, then the traveling wave of pain signal will be largely reflected back and only partially transmitted to the brain, hence pain relief can be achieved. (2) If the impedance of the meridian entirely matches that of the pain source after acupuncture, then the pain source would appear to be nonexistent to the brain, hence analgesia can be achieved. The former mechanism can be used to explain the relief for chronic pain and the latter one for acute pain. It is believed that the proposed mechanisms via match or mismatch of the impedances can explain how the acupuncture works not only in the treatment of pain, but also in various other therapies of Part 3.