subject: Research Of Biological Bases Of Acupuncture. [print this page] Finding the physiological pathway of acupuncture is a long-standing goal. Relevant investigation seems to have taken two path ways. These involve searching for the biochemical markers that respond to acupuncture needling, and for the biomedical models that can describe the phenomena found in acupuncture treatment. Although each path is notable for its promise, each has been constrained by the problems of its methods. The first path has led to various identifications of acupuncture-associated biomarkers, including, for instance, antinociceptive endogenous opioids and fMRI-detected brain activity. Findings on biomarkers, however, are more revealing of correlations than mechanisms. The second path which is more aimed at identifying mechanisms involves a search for biochemical foundation of acupuncture phenomena, e.g., acupuncture points. Queries guiding these research efforts include, for example: do meridians have a physical basis and what is the nature of acupuncture signals they carry?
Although no specific anatomical structure, e.g., a specialized type of nerve ending, has been located at cutaneous nerves corresponding to acupuncture points, several studies have described an association of known morphological structures with acupoints. A large proportion of traditional acupoints have been identified as locations at which underlying nerve-vessel bundles wrapped in a loose sheath of connective tissue penetrate the fascia to reach the outer dermal layers. A subsequent study of 24 acupoints on six meridians indicated a high concordance between the locations of acupoints and the location of loose connective tissue planes. Acupuncture point structures have been reported in studies utilizing high-intensity ultrasound, with ovoid images being proposed as acupuncture points localized in connective tissue. Taking into account the several study findings suggestive of a connective tissue basis for acupuncture points, the oft-cited findings that injection of anesthetic into an acupoint obstructs responsiveness of the point to needle stimulation should be reexamined on connective tissues.
Among most research intended for classifying acupoints, electrodermal activity continues as one of the most often examined outcomes. Measurement of such activities reveal acupuncture points as the peaks of individually contoured conductivity fields. New systematic reviews have examined studies comparing acupuncture points with nonacupoints in healthy volunteers. Five of the nine studies reviewed showed a positive association for acupoints as sites of lower electrical impedance. Additionally, patterns of fMRI signals have been detected following acupuncture therapy that are distinct from patterns provoked by simple sensory stimulation. However, while detection of brain activity consequent to needle stimulation indicates that the brain is an endogenous monitor of acupuncture actions, it does not necessarily follow the logic that neurological activity is the initiator of such physiological actions.
As mentioned earlier, considerable evidence has built up for a connective tissue-based system being an alternative mediator of acupuncture activity. Evidences of superficial fascia as the initial response factor to needle stimulation include a visible wrapping of collagen fibers around the needle that might elucidate the needle grasp phenomenon of acupuncture practice, in addition to a weakening of clinical responses to needling after injection of collagenase at acupoints. Observations that needling also stimulates regional changes in blood flow, that may result from acupuncture-related peripheral increases in nitric oxide as an intermediary signal molecule between connective tissue and sensory nerve endings need further research to clarify the progression of events underlying the mechanism of acupuncture stimulation to acupuncture signaling. In general, scientific investigators in the world have developed various well-designed models that depict scientifically-sound pathways for mapping the biological networks for acupuncture.
