The mechanism of acupuncture analgesia: a review

In order to better understand the therapeutic effectiveness of acupuncture, questions about the means by which it operates need to be addressed. This article provides an overview of the neural, humoral and biomagnetic mechanisms that may contribute to the production of acupuncture analgesia. The concordance of some acupuncture points and trigger points is noted. Possible modulatory areas within the central nervous system are considered and parallels between the influence of acupuncture and the theory of diffuse noxious inhibitory control are explored. The concurrence of peripheral and central nervous activity with acupuncture stimulation suggests a functional if not an anatomical relationship between acupuncture points, meridians, and the nervous system. In addition, many studies demonstrate that acupuncture activates endogenous substances which inhibit nociceptive transmission. Two alternative theories are examined: that acupuncture analgesia occurs as part of a generalized stress response or as a result of an individual's suggestibility. At a practical level, the choice o f stimulation modality may influence clinical outcome, as different forms of stimulation, e.g. electroacupuncture and transcutaneous electrical nerve stimulation, can invoke subtly different pathways to produce analgesia. Future studies of the clinical effectiveness of acupuncture could be enhanced by using physiological measurement to assess both process and outcomes. This may also help in providing effective, individualized treatment.