Acupuncture is a traditional Chinese technique that has been used for thousands of years to treat chronic pain and other health problems associated with inflammation. It is also used today to relieve a number of ailments such as depression, epilepsy, schizophrenia or chronic pain. This method would even reduce hot flashes for postmenopausal women.

Acupuncture is effective in some parts of the body but not in others

The scientific basis for this technique is still poorly understood. In a new study published October 13 in the journal temper natureNeuroscience researchers at Harvard Medical School have succeeded in elucidating the basic 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 needed for acupuncture to work occur only in a specific area of ​​the hind limb region. “This would explain why acupuncture is successful in the hind limbs, as opposed to acupuncture in the abdomen.‘, point to the researchers.

Dealing with the cytokine storm

The researchers were primarily interested in the cytokine storm, which often causes acute systemic inflammation and which can result from many factors such as Covid-19, cancer treatment or sepsis. “This excessive immune response is a major medical problem with a very high mortality rate of 15% to 30%., notes Qiufu Ma, professor of new biology and lead author of the study. There are no medications to treat cytokine storm. Acupuncture releases nerve signals that affect the work of other parts of the body, including organs, and thus can treat this problem.

Researchers build on a 2014 study published in nature medicineScientists report that electro-acupuncture, a modern version of traditional acupuncture that uses electrical stimulation, can reduce a cytokine storm in mice. This happens through activation of the vagal-adrenal axis, a pathway in which the vagus nerve sends signals to the adrenal glands to release dopamine.

Then this research was supplemented with the latest publication in 2020 in the journal neuronHarvard researchers found that this effect of electro-acupuncture is region-specific. It is effective when administered to the hind limb area, but has no effect when administered to the abdominal area. The team hypothesized that there might be sensory neurons specific to the hind limb area responsible for this difference in response.

Understand the areas to target

In their new study, the researchers conducted a series of experiments on mice to investigate this hypothesis. First, they identified a small subset of sensory neurons that were marked by the expression of the PROKR2Cre receptor. They found that the number of these neurons is three to four times more in the tissues of the deep fascia of the hind limb than in the fascia of the abdomen.

Then they tested this in mouse models that lack these sensory neurons. They found that electroacupuncture in the hind limbs did not activate the adrenal axon. 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 activates the adrenal axon in a manner similar to electroacupuncture. “Essentially, the activation of these neurons is both necessary and sufficient to activate the adrenal axon.Qiufu Ma continues.

In a recent experiment, the scientists discovered 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, which leads to a stronger response to electrical acupuncture in the anterior region. “Based on this distribution of nerve fibers, we can roughly predict where electrical stimulation will be effective and where it will not., Qiufu Ma’s conclusion.

Clinical tests on humans

Together, these results provideThe first concrete neuroanatomical explanation for the selectivity and specificity of acupuncture points, the lead author of the study appreciated. They tell us the parameters of acupuncture, so where to go, how far to go, what intensity should be. Although these results were obtained in mouse models, it is believed that the same results are expected in humans. The next step will be clinical testing of electroacupuncture in humans with inflammation caused by a real infection such as Covid-19.