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Vagus Nerve

Acupuncture May Reduce Inflammation via Vagus Nerve Pathways

Acupuncture's anti-inflammatory powers may be driven by the vagal-adrenal axis.

Key points

  • Acupuncture is a traditional Chinese medicine technique used to treat chronic pain and illnesses associated with systemic inflammation.
  • Eastern medicine views acupuncture as a way to redirect the flow of "life force" or vital "Qi energy" along meridian pathways within the body.
  • Western medical researchers recently identified how acupuncture triggers an anti-inflammatory response via autonomic vagus nerve pathways.
This stock photo shows electroacupuncture being used in a clinical practice. This modern-day form of acupuncture augments traditional methods by passing a microcurrent of electricity through very thin needles during therapeutic treatments.
Source: Pordee_Aomboon/Shutterstock

Acupuncture has been around for thousands of years. But, until recently, Western scientists have struggled to pinpoint its neuroanatomical mechanisms. Accumulating evidence sheds light on how painlessly inserting tiny needles (no wider than a strand of hair) through the skin at strategic "trigger points" can reduce inflammation in humans and mouse models.

Despite being a commonly used Complementary and Alternative Medicine (CAM) treatment, 21st-century researchers and doctors still have a relatively poor understanding of how acupuncture activates the autonomic nervous system in ways that can reduce systemic inflammation.

For the past few years, a team of researchers at Harvard Medical School (HMS) led by Qiufu Ma has been conducting experiments in mice designed to elucidate the neuroanatomical underpinnings of acupuncture's anti-inflammatory effects.

How Was Acupuncture First Used?

Before we dive into the latest (2021) research findings from Harvard's Ma Lab, let's trace the footprints of acupuncture's ancient origins. In Eastern medicine, acupuncture was conceived millennia ago as a way to hack into the body's yin-yang dynamics and balance the flow of Qi energy (a.k.a. "Chi power") along different meridian pathways.

Acupuncture techniques were first described in written texts about 2,121 years ago and were practiced for centuries in Asia before being embraced by Western practitioners of integrative medicine.

In their 2004 Rheumatology paper, "A Brief History of Acupuncture," Adrian White and Edzard Ernst write, "The concepts of channels (meridians or conduits) in which the Qi (vital energy or life force) flowed were well established by [100 BCE], though the precise anatomical locations of acupuncture points developed later."

Through the lens of Western medicine, the push-pull dynamics between the parasympathetic ("rest and digest") branch and the sympathetic ("fight or flight") branch can be viewed as a type of yin-yang interaction within our autonomic nervous system.

Notably, vagus nerve stimulation (VNS) is a well-established way to activate the parasympathetic nervous system in ways that counteract fight-or-flight stress responses. (See, "Vagus Nerve Stimulation via the Outer Ear Takes Center Stage.")

This medically accurate illustration shows how the vagus nerve (CN X) wanders throughout the body. Vagus means "wandering" in Latin. Vagal means "relating to the vagus nerve."
Source: SciePro/Shutterstock

Acupuncture Activates Inflammation-Regulating Pathways via the Vagus Nerve

Qiufu Ma is a neurobiologist who studies the fundamental mechanisms of pain and has been curious about the biological underpinnings of acupuncture for many years. About seven years ago, Ma's curiosity about how the vagus nerve might mediate acupuncture's anti-inflammatory potential was piqued by a paper (Torres-Rosas et al., 2014) which found that using electroacupuncture to stimulate the vagal-adrenal axis alleviated systemic inflammation in mice. His curiosity was "further intensified" by research (Koopman et al., 2016) published in PNAS by Kevin Tracey and colleagues at the Feinstein Institute for Medical Research showing that vagus nerve stimulation tames inflammatory responses and lessens rheumatoid arthritis symptoms in humans. (See, "Vagus Nerve Stimulation Dramatically Reduces Inflammation.")

Last year, Ma's team successfully used an electroacupuncture technique to calm "cytokine storms" in mice with systemic inflammation. This study established that activating somatosensory autonomic reflexes plays a vital role in how electroacupuncture stimulation (ES) reduces systemic inflammation. These findings (Liu et al., 2020) were published in the peer-reviewed journal Neuron. In a follow-up study (Liu et al., 2021), Ma and his HMS colleagues unearthed a neuroanatomical basis for how electroacupuncture reduces inflammation. This ES study in mice pinpoints a specific subset of sensory neurons that appear to trigger an anti-inflammatory response via the vagal-adrenal axis. "Here we show that PROKR2Cre-marked sensory neurons are crucial for driving the vagal-adrenal axis," the authors explain. These findings were published on October 13 in the peer-reviewed journal Nature.

"This study touches on one of the most fundamental questions in the acupuncture field: What is the neuroanatomical basis for body region, or acupoint, selectivity?" Ma said in a news release. "[Our findings] provide the first concrete, neuroanatomic explanation for acupoint selectivity and specificity." He also notes that this research helps define electroacupuncture's parameters by elucidating "where to go, how deep to go, how strong the intensity should be."

Although these vagal-adrenal axis acupuncture studies were done using mouse models, Ma clarifies that "the basic organization of neurons is likely evolutionarily conserved across mammals, including humans."

That said, more research is needed. The next step for Ma and his colleagues is to conduct human experiments to see if our vagal-adrenal axis responds to electroacupuncture in the same ways they've observed using animal models.


Shenbin Liu, Zhifu Wang, Yangshuai Su, Lu Qi, Wei Yang, Mingzhou Fu, Xianghong Jing, Yanqing Wang & Qiufu Ma. "A Neuroanatomical Basis for Electroacupuncture to Drive the Vagal–Adrenal Axis." Nature (First published: October 13, 2021) DOI: 10.1038/s41586-021-04001-4

Shenbin Liu, Zhi-Fu Wang, Yang-Shuai Su, Xiang-Hong Jing, Yan-Qing Wang, Qiufu Ma. "Somatotopic Organization and Intensity Dependence in Driving Distinct NPY-Expressing Sympathetic Pathways by Electroacupuncture." Neuron (First published: August 12, 2020) DOI: 10.1016/j.neuron.2020.07.015

Frieda A. Koopman, Sangeeta S. Chavan, Sanda Miljko, Simeon Grazio, Sekib Sokolovic, P. Richard Schuurman, Ashesh D. Mehta, Yaakov A. Levine, Michael Faltys, Ralph Zitnik, Kevin J. Tracey, and Paul P. Tak. "Vagus Nerve Stimulation Inhibits Cytokine Production and Attenuates Disease Severity in Rheumatoid Arthritis." PNAS (First published: July 05, 2016) DOI: 10.1073/pnas.1605635113

Rafael Torres-Rosas, Ghassan Yehia, Geber Peña, Priya Mishra, Maria del Rocio Thompson-Bonilla, Mario Adán Moreno-Eutimio, Lourdes Andrea Arriaga-Pizano, Armando Isibasi & Luis Ulloa. "Dopamine Mediates Vagal Modulation of the Immune System by Electroacupuncture." Nature Medicine (First published: February 23, 2014) DOI: 10.1038/nm.3479

Adrian White and Edzard Ernst. "A Brief History of Acupuncture." Rheumatology (First published: May 05, 2004) DOI: 10.1093/rheumatology/keg005

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