by Alida May
There are six main physiological effects of acupuncture that have been studied
in recent research.
Acupuncture is the insertion of thin needles into specific points in the skin for therapeutic benefit.
As acupuncturists we generally use the Eastern explanatory model to diagnose and treat patients. It is an ancient, all-encompassing theory that has developed over thousands of years, and is still developing. It allows us to work out which points and techniques will be most beneficial for the individual patient.
As acupuncture becomes more mainstream in the West it becomes increasingly important to be able to explain acupuncture using the Western medical model. Here I will outline some research which
demonstrates some of the underlying mechanisms.
There are six main physiological effects of acupuncture that have been studied in recent research.
1. Anti-inflammatory Effect
Low level inflammation in the body is a biochemical mechanism that can lead to a huge number of chronic diseases. Recent research has reported possible anti-inflammatory effects of acupuncture through a complex neuro-endocrino-immunological network of actions. Mediated by sympathetic and parasympathetic pathways, effects include the down-regulation of pro-inflammatory cytokines[i].
2. Modulation of Heart Rate Variability
Heart Rate Variability (HRV) describes the beat-to-beat fluctuations in the rhythm of the heart. Low HRV is associated with increased risk of all-cause mortality[ii]. A recent systematic review[iii] gives evidence of the possible effect of acupuncture on modulating the Low Frequency of HRV in both healthy and non-healthy individuals.
3. Mu-opioid Receptors
The opioid system in the body controls pain, reward and addictive behaviour. Opioids exert their pharmacological actions through receptors, one of which is the mu-opioid receptor (MOR). Acupuncture has been shown to evoke short-term increases in MOR binding potential in multiple pain and sensory regions of the brain, and evoke long-term increases in MOR binding potential in some of the same structures[iv].
4. Purinergic Signaling
Purinergic signalling is a form of extra-cellular signalling that regulates cellular function. It is mediated by purine nucleosides and nucleotides such as adenosine, a neuromodulator believed to play a role in promoting sleep, suppressing arousal, and regulating blood flow to various organs. Acupuncture has been shown to trigger increases in interstitial adenosine which can reduce the severity of chronic pain (adenosine-mediated antinociception)[v].
5. Hypothalamus-Pituitary-Adrenal (HPA) Axis
The HPA axis is the physical network through which the body responds to stress.
This system can easily become disrupted, which in turn can lead to a wide range of symptoms - from hormonal imbalances, to sleep disturbances and digestive disruptions. Based on neuro-imaging results, acupuncture is thought to improve the function of the HPA[vi].
6. Brain Activity
Again, using neuro-imaging results, acupuncture was shown to increase the activity of somatosensory and cognitive pain processing areas of the brain[vii], also in the affective processing areas of the brain[viii]. During the post-acupuncture period more complex neural responses are recorded, showing the effect of acupuncture as a function of time[ix].
How Does Acupuncture Mediate these Effects?
Fascia is non-specialised connective tissue that envelops all muscles, nerves, bones, lymphatics and blood vessels in the body. One could draw a line between any two points of the body via a path of fascia. Many systems of the body may be affected by mechanical changes in the fascia, for example changes in tissue tension could affect the function of all the structures mentioned above.
Mechanotransduction is the mechanism by which cells convert mechanical stimulus into chemical activity. Prolonged stretching of the fascia causes certain cells to change shape, triggering a certain cellular response which can lead to a whole range of reactions[x]. Connective tissue itself has also recently been shown to contain its own sensory nerve endings[xi].
Rotating an inserted acupuncture needle causes the connective tissue to wrap around the needle[xii]. The fascia is stretched for a prolonged period of time, causing significant mechanical and chemical effects within the body such as the release of ATP which, when converted to adenosine, can act as a local analgesic[xiii].
Acupuncture meridians many be related to connective tissue as they are mainly located along connective tissue planes[xiv]. Since loose connective tissue houses blood vessels and nerves, this suggests that mechanical stimulation of connective tissue by an acupuncture needle could transmit a mechanical signal to sensory nerves, as well as directly innervating connective tissue. [xv]
Acupuncture is thought to modulate endogenous regulatory systems, such as the sympathetic nervous system, endocrine system, and the neuroendocrine system[xvi]. In other words, the body has its own healing / regulatory systems that acupuncture is able to stimulate or activate, thus supporting the body to move towards health.
[i] McDonald, J. L., Cripps, A. W., Smith, P. K., Smith, C. A., Xue, C. C., & Golianu, B.
(2013). The Anti-Inflammatory Effects of Acupuncture and Their Relevance to
Allergic Rhinitis: A Narrative Review and Proposed Model. Evidence-Based
Complementary and Alternative Medicine, 2013(4), 1–12. doi:10.1007/s00424-
[ii] Anderson, B., Nielsen, A., McKee, D., Jeffres, A., & Kligler, B. (2012).
Acupuncture and Heart Rate Variability: A Systems Level Approach to
Understanding Mechanism. Jsch, 8(2), 99–106. doi:10.1016/j.explore.2011.12.002
[iii] Chung, J. W. Y., Yan, V. C. M., & Zhang, H. (2014). Effect of Acupuncture on
Heart Rate Variability: A Systematic Review. Evidence-Based Complementary and
Alternative Medicine, 2014(5), 1–19. doi:10.1111/j.1365-2982.2008.01164.x
[iv] Harris, R. E., Zubieta, J.-K., Scott, D. J., Napadow, V., Gracely, R. H., & Clauw, D.
J. (2009). Traditional Chinese acupuncture and placebo (sham) acupuncture are
differentiated by their effects on μ-opioid receptors (MORs). NeuroImage, 47(3),
[v] Takano, T., Chen, X., Luo, F., Fujita, T., Ren, Z., Goldman, N., et al. (2012).
Traditional Acupuncture Triggers a Local Increase in Adenosine in Human
Subjects. The Journal of Pain, 13(12), 1215–1223. doi:10.1016/j.jpain.2012.09.012
[vi] Cho, Z. H., Hwang, S. C., Wong, E. K., Son, Y. D., Kang, C. K., Park, T. S., et al.
(2006). Neural substrates, experimental evidences and functional hypothesis of
acupuncture mechanisms. Acta Neurologica Scandinavica, 113(6), 370–377.
[vii] Usichenko, T. I., Wesolowski, T., & Lotze, M. (2014). Verum and sham
acupuncture exert distinct cerebral activation in pain processing areas: a
crossover fMRI investigation in healthy volunteers. Brain Imaging and Behavior.
[viii] Huang, W., Pach, D., Napadow, V., Park, K., Long, X., Neumann, J., et al.
(2012). Characterizing acupuncture stimuli using brain imaging with FMRI–a
systematic review and meta-analysis of the literature. PLoS ONE, 7(4), e32960.
[ix] Hui, K. K., Liu, J., Makris, N., Gollub, R. L., Chen, A. J., Moore, C. I., et al. (2000).
Acupuncture modulates the limbic system and subcortical gray structures of the
human brain: evidence from fMRI studies in normal subjects. Human Brain
Mapping, 9(1), 13–25.
[x] H.M. Langevin et al., “Mechanical signaling through connective tissue: A
mechanism for the therapeutic effect of acupuncture,” FASEB J, 15:2275-82,
[xi] T. Taguchi et al., “Dorsal horn neurons having input from low back structures
in rats,” Pain, 138:119-29, 2008
[xii] H.M. Langevin et al., “Mechanical signaling through connective tissue: A
mechanism for the therapeutic effect of acupuncture,” FASEB J, 15:2275-82,
[xiii] N. Goldman et al., “Adenosine A1 receptors mediate local anti-nociceptive
effects of acupuncture,” Nat Neurosci, 13:883–88, 2010.
[xiv] H.M. Langevin, J.A. Yandow, “Relationship of acupuncture points and
meridians to connective tissue planes,” Anat Rec, 269:257-65, 2002.
[xv] Langevin, H. M. (2014). Acupuncture, connective tissue, and peripheral
sensory modulation. Critical Reviews in Eukaryotic Gene Expression, 24(3),
[xvi] Stener-Victorin, E., & Wu, X. (2010). Autonomic Neuroscience: Basic and
Clinical. Autonomic Neuroscience: Basic and Clinical, 157(1-2), 46–51.