The polymodal receptor hypothesis of acupuncture and moxibustion, and its rational explanation of acupuncture points

The participation of polymodal-type receptor (PMR) in the action of acupuncture and moxibustion (A&M) was briefly reviewed and a working hypothesis was proposed. The PMR is known as a kind of nociceptor, and is responsive to mechanical (acupuncture), thermal (moxibustion) and chemical stimuli, and its sensory terminals are free nerve endings and exist in various tissues of the entire body. Selective activation of the PMR produced the de-qi sensation (a kind of deep pain) and neurogenic inflammation (flare and wheal), and considered as an input of the endogenous pain inhibition, autonomic, immune and endocrine functions. These characteristics of PMR are in agreement with a possible candidate of A&M. One of the functional characteristics of acupuncture points is its tenderness (ah-shi points) and its close relation to the trigger points. The sensitization of PMR is suggested to be the major cause of formation of trigger points, so if one chooses the acupuncture (trigger) points as the treatment loci, the sensitized PMR are activated more easily by gentle A&M procedures and activate various bio-regulatory systems more effectively. Thus, the present PMR hypothesis offers a rational explanation of functional meanings of the acupuncture (trigger) points.