Neural Mechanisms of Acupuncture Analgesia

Neural Mechanisms of Acupuncture Analgesia

Acupuncture in the early 1970s immediately ran into two major obstacles. The first was high expectation from the public. The second was the lack of a theory to explain what went on physiologically and pathologically in the body after the insertion of the needles. As pointed out earlier, one of the biggest challenges is to learn whether the traditional Chinese theory of acupuncture is close to the truth or not. We have to first translate the ancient archaic language into the ordinary tongue or the 21st century scientific terms. But meridian is invisible in our anatomy and cannot be explained by present-day physiology. We do not know what qi is. The concept of de qi is not well defined. To handle this lack of precision, a standard description of feeling “soreness, numbness, heaviness and distension” by the patient is employed. For a large number of researchers, the meridians may be conceived as a functional but not anatomical concept. They may summarize multiple physiological functions including the circulatory, endocrine, nervous, and immune systems. Since meridian and qi are not observable, most of the research since 1970 has focused on the neural based mechanisms.

Let us summarize this field based on a recent review: (1) Traditional Chinese (verum) acupuncture analgesia is manifest only when de-qi concurs. (2) Afferent nerve fibers are activated in manual or electrical acupuncture. (3) It is an integrated process at different levels of the central nervous system (CNS) between impulses from acupoints and afferent signaling from painful regions. (4) Spinal pathways of acupuncture impulses from acupoints ascend mainly through the ventrolateral funiculus. Most of sensory nuclei such as the nucleus raphe magnus (NRM) and the nucleus reticularis gigantocellularis (Rgc) are constitutive parts of the endogenous descending inhibitory system in CNS. (5) Opioid peptides and glutamate are implicated. (6) Effectiveness of acupuncture, without adjunct drugs for surgery is not satisfactory. (7) Acupuncture is effective in treating chronic pain. (8) Conflicting results of acupuncture are caused by activation of different afferent nerve fibers. Central to these models is the participation of the afferent nerve fibers and CNS. Recent research has moved to pain control and brain imaging.

Source: Edward S. Yang, Pei-Wen Li, Bernd Nilius, and Geng Li^. Ancient Chinese medicine and mechanistic evidence of acupuncture physiology. Pflugers Arch. Nov 2011; 462(5): 645–653.