Spinal mechanism of acupuncture-induced analgesia

Abstract

shown that both manual and electroacupuncture (EA) act through stimulation of group III and IV somatic afferent nerves to significantly modulate both sympathetic and parasympathetic outflow and hence cardiovascular function. EA evokes input in hypothalamic, midbrain and medullary regions as well as the dorsal horn and intermediolateral regions of the spinal cord and through the actions of a number of neurotransmitters, including endorphins, enkephalins, endocannabinoids, γ-aminobutryic acid and glutamate, among others, such stimulation can lower elevated and raise depressed blood pressure. Low frequency EA applied to acupoints overlying the median (pericardial meridian, P5 and P6) and deep peroneal (stomach meridian ST36 and ST37) nerves appears to be most effective. Using insights gained from experimental investigations, compared to sham stimulation of ineffective acupoints, EA at P5-P6 and ST36-ST37 has been shown to be capable of reducing systolic and diastolic blood pressures in ~ 70% of a small group of patients with mild to moderate hypertension, when it is applied for 30 min once weekly for eight weeks. The onset of action is slow, requiring 4–6 weeks, but is prolonged, in part, due to the actions of enkephalin in the rostral ventrolateral medulla. Although, we now have insight into many of acupuncture’s mechanisms more work is required to determine if non-responders can be converted to responders and if EA can chronically lower BP in hypertensive patients.