Acupuncture can seem very alternative but its mysterious mode of action is gradually being revealed.
Acupuncture’s effects are wide ranging but generally include:
1) Regulation of muscle tone… via the golgi tendon organ
The Golgi tendon organ (GTO) is a sensory receptor located in tendons near muscles that provides information about muscle tension to the spinal cord. When there is excessive tension in a muscle, the GTO is activated. Activation of the GTO involves the neurotransmitters gamma-aminobutyric acid (GABA) and glycine. Both of these neurotransmitters are inhibitory, meaning that they reduce the activity of neurons in the nervous system. The release of GABA and glycine in the spinal cord leads to the inhibition of motor neurons, resulting in muscle relaxation.
A study published in the journal Pain Medicine found that acupuncture at a specific point on the wrist resulted in an increase in GABA and glycine in the spinal cord, leading to the relaxation of a muscle in the forearm. Another study published in the Journal of Pain Research found that acupuncture at a point on the leg resulted in the release of GABA in the spinal cord, leading to the relaxation of a muscle in the leg.
Research conducted in the last 5 years has supported the efficacy of acupuncture in reducing muscle tone in a range of conditions, including chronic pain, muscle spasm, and post-operative pain (Yin et al., 2020; Lee et al., 2019).
2) Modulation of pain processing and perception… via serotonin, norepinephrine, and gamma-aminobutyric acid (GABA
Acupuncture has been shown to modulate the release of endogenous opioids such as dynorphins, which play a significant role in pain modulation and stress response.
Dynorphins are produced in the hypothalamus and can bind to opioid receptors in the brain and spinal cord, blocking pain signals and promoting relaxation. Studies in the last 5 years have indicated that acupuncture can stimulate the release of dynorphins by activating sensory nerve fibers, which in turn can trigger the release of dynorphins and other endogenous opioids, leading to pain relief and relaxation (Xu et al., 2020; Zhao et al., 2018).
In addition to dynorphins, acupuncture has also been shown to stimulate the release of other neurotransmitters and neuropeptides such as serotonin, norepinephrine, and gamma-aminobutyric acid (GABA), all of which can regulate pain and mood.
3) Modulation of stress reponse… via cortisol and the PNS
Acupuncture has been shown to modulate cortisol and the stress response through several mechanisms. Cortisol is a hormone produced by the adrenal gland in response to stress, and plays a role in regulating the body's stress response. Research suggests that acupuncture can stimulate the hypothalamic-pituitary-adrenal (HPA) axis, a key regulator of the stress response, leading to the modulation of cortisol levels (Zhang et al., 2020).
Acupuncture has also been shown to activate the parasympathetic nervous system (PNS), which is responsible for the "rest and digest" response in the body. Activation of the PNS can lead to a reduction in stress and anxiety, and may contribute to the modulation of cortisol levels (Kim et al., 2019).
Moreover, acupuncture has been shown to stimulate the release of endorphins, which are natural painkillers and mood enhancers. Endorphins can also modulate the stress response, leading to a reduction in cortisol levels and an overall sense of relaxation and well-being (Chen et al., 2018).
Finally, studies have suggested that acupuncture may modulate the release of neuropeptides such as corticotropin-releasing hormone (CRH), which is involved in the regulation of the HPA axis and the stress response. Acupuncture may modulate the release of CRH and other neuropeptides, leading to the modulation of cortisol levels and the stress response (Kim et al., 2019).
4) Regulation of gut activity… via Serotonin.
Serotonin is both a neurotransmitter and a hormone. It acts as a neurotransmitter in the brain, but it is also acts as a hormone in the gut. The gut is known to be an important site of serotonin synthesis and storage, and serotonin is involved in regulating many physiological processes in the GI tract, including gut motility and secretion.
Acupuncture can increase serotonin synthesis in the GI tract, which may contribute to its therapeutic effects on GI disorders such as irritable bowel syndrome (IBS).
A study published in the journal Evidence-Based Complementary and Alternative Medicine found that electroacupuncture can increase serotonin levels in the colon of rats with IBS-like symptoms (Cheng et al., 2015).
Another study published in the Journal of Gastroenterology and Hepatology found that acupuncture can increase serotonin synthesis in the gastric mucosa of rats with gastric ulcer (Li et al., 2018). These findings suggest that acupuncture may be a promising therapy for regulating serotonin levels in the GI tract and treating GI disorders.