This traditional medicinal method requires the presence of certain neurons in order to trigger an anti-inflammatory response.
- Acupuncture triggers nerve signaling that would treat the cytokine storm that is causing severe systemic inflammation.
- Acupuncture works well in the hind limbs but not in the abdomen.
Acupuncture is a traditional Chinese technique that has been used for millennia to treat chronic pain and other health conditions associated with inflammation. It is also used today to relieve a number of illnesses such as depression, epilepsy, schizophrenia and chronic pain. This method would even reduce hot flashes for postmenopausal women.
Acupuncture works on some parts of the body and not others
The scientific basis of this technique remains poorly understood. In a new study, published on October 13 in the journal Nature, neuroscientists at Harvard Medical University have successfully elucidated the underlying neuroanatomy of acupuncture that activates a specific signaling pathway. They identified a subset of neurons that must be present for acupuncture to trigger an anti-inflammatory response via this signaling pathway.
Scientists have determined that the neurons necessary for the effectiveness of acupuncture occur only in a specific area of the hind limb region. “This would explain why acupuncture in the hind limbs works, unlike acupuncture in the abdomen.”, point out the researchers.
Treating Cytokine Storm
The researchers were primarily interested in cytokine storm, which frequently causes severe systemic inflammation and can be triggered by many factors such as Covid-19, cancer treatment or sepsis. “This exuberant immune response is a major medical problem with a very high mortality rate of 15% to 30%underlines Qiufu Ma, professor of neurobiology and lead author of the study. Drugs to treat cytokine storm are lacking.” Acupuncture triggers nerve signaling that affects the functioning of other parts of the body, including organs, and thus could treat this problem.
The researchers rely on a 2014 study, published in NatureMedicine, in which scientists reported that electroacupuncture, a modern version of traditional acupuncture that uses electrical stimulation, could reduce cytokine storm in mice. This happens through activation of the vagal-adrenal axis, a pathway in which the vagus nerve signals the adrenal glands to release dopamine.
This research was then supplemented by another, published in 2020 in the journal Neuron, where Harvard researchers found that this electroacupuncture effect is region-specific. It is effective when administered in the hind limb region, but has no effect when administered in the abdominal region. The team hypothesized that there might be sensory neurons unique to the hindlimb region responsible for this difference in response.
Understand the areas to target
In their new study, the researchers conducted a series of experiments in mice to investigate this hypothesis. First, they identified a small subset of sensory neurons marked by expression of the PROKR2Cre receptor. They determined that these neurons are three to four times more numerous in the tissue of the deep fascia of the hind limb than in the fascia of the abdomen.
They then tested this on mouse models that lack these sensory neurons. They found that electroacupuncture in the hind limbs did not activate the vagal-adrenal axis. In another experiment, the team used light-based stimulation to directly target these sensory neurons in the deep fascia of the hind limb. This stimulation activated the vagal-adrenal axis in a manner similar to electroacupuncture. “Basically, the activation of these neurons is both necessary and sufficient to activate this vagal-adrenal axis.”, continues Qiufu Ma.
In a final experiment, the scientists explored the distribution of neurons in the hind limb. They found that there are many more neurons in the anterior muscles of the hind limb than in the posterior muscles, resulting in a stronger response to electroacupuncture in the anterior region. “Based on this nerve fiber distribution, we can almost accurately predict where electrical stimulation will be effective and where it will not.”, concluded Qiufu Ma.
Clinical tests on humans
Together, these results provide “the first concrete neuroanatomical explanation of the selectivity and specificity of acupuncture pointsestimated the main author of the study. They tell us the parameters of acupuncture, so where to go, how deep to go, what the intensity should be..” Although these results were obtained on mouse models, he believes that the same results are to be expected in humans. The next step will be clinical trials of electroacupuncture in humans with inflammation caused by real-world infections such as Covid-19.
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