Acupuncture Analgesia: A Review of Its Mechanisms of Actions

Abstract

The mechanism of acupuncture analgesia (AA) has been widely explored since the 1970s. Early studies investigated the relationship between acupuncture and endogenous opiates (beta-endorphin, enkephalin, endomorphin and dynorphin). Before the 1990s, most experts agreed on the concept that in normal animal models, lower frequency electroacupuncture (EA) stimulates the release of beta-endorphin, enkephalin and endomorphin, which in turn activates the mu- and delta-opioid receptors, and that higher frequency EA stimulates dynorphin which activates the kappa-opioid receptor. Besides endogenous opiates, our studies have focused on serotonin. The serotoninergic descending inhibitory pathway is suggested to be an important mechanism of acupuncture analgesic, collaborating with endogenous opiates. Many efforts have been made to clarify these mechanisms, but to date no satisfactory consensus has been reached. In the late 1990s, researchers began to focus on the different analgesic effects of EA between normal and hyperalgesic animal models. Published data from these studies imply that normal and hyperalgesic animals respond differently to EA. Results from experiments on the anti-hyperalgesia effect of EA have raised a new issue about the influences of EA on receptors to excitatory amino acid in the spinal cord level. Results from various studies have shown that these receptors play a role in the mechanism of AA. Recently, research on the autonomic nervous system (ANS) seem to indicate its connection with acupuncture. The inflammatory reflex (via the ANS) might be a crucial part of anti-hyperalgesia elicited by acupuncture, and this reflex, which regulates the immune system in the organism, can elucidate not only the mechanism of AA but also the mechanism of acupuncture applied to other inflammatory conditions. Innovation of functional image study enables us to analyze the responses of cortex on living human body to acupuncture. However, results of these experiments are still controversial. After 30 years of acupuncture research, there are still many puzzles left to be solved regarding the mechanism of AA.

Effect of aquapuncture on postoperative analgesia after ovariohysterectomy in dogs

“…A major part of studies investigating the effect of AP have been related to pain assessment and the possible mechanisms behind the acupuncture analgesic effects have been reported elsewhere (CAO, 2002;HE, 1987;CHEN, 2008;MCLENNAN et al, 1977;KAVOUSSI;ROSS, 2007;MELZACK, 1976;MOON et al, 2007;OKADA;KAWAKITA, 2009;TAGUCHI, 2008;ZIJLSTRA et al, 2003). Acupuncture has been commonly used to treat acute and chronic pain (CAO, 2002;CASSU et al, 2008;FERRARI et al, 2006;HE, 1987;JOAQUIM et al, 2010;TAGUCHI, 2008).…”

“…Acupuncture analgesia embraces the majority of the pain mechanisms, like transduction, transmission, modulation and perception, involving an anti-inflammatory, humoral and neurological effect (CAO, 2002;HE, 1987;KAVOUSSI;ROSS, 2007;CHEN, 2008;MCLENNAN et al, 1977;MELZACK, 1976;MOON et al, 2007;OKADA;KAWAKITA, 2009;TAGUCHI, 2008;ZIJLSTRA et al, 2003). Both opioids and acupuncture activate inhibitory descending pathways in the spinal cord and prevent noxious stimuli to reach the brain CHEN, 2008).…”

The Potential Role for Acupuncture in Treating Symptoms in Patients with Lung Cancer: An Observational Longitudinal Study

“…Acupuncture practitioners recognize meridians or energy pathways that correspond to neurovascular connective tissue planes connecting various parts of the body [30][31][32][33] . One hypothesis is that acupuncture stimulates a somatosensory system that results in the release of endogenous opioids 34,35 .…”

Effects of Acupuncture on Sensory Perception: A Systematic Review and Meta-Analysis

“…Brain imaging studies have shown that acupuncture alters activation patterns in brain areas associated with pain processing [9]. It is postulated that in response to the needle stimulation mechanisms of the endogenous pain modulation such as diffuse noxious inhibitory controls (DNIC), segmental inhibition, and descending pain control pathways lead to a decrease in pain perception [10,11]. At this, various centrally and/or peripherally acting neuromodulators and neurotransmitters such as endorphins [12], serotonin [13], ATP [14], etc.…”