Neural circuit mechanisms of acupuncture effect: where are we now?

Acupuncture, an ancient practice of traditional Chinese medicine, has increasingly been integrated into modern medicine as an effective complementary therapy for a variety of health conditions. This technique, which involves inserting fine needles at specific points on the body, has attracted considerable scientific interest, particularly with advances in neuroscience. Understanding how acupuncture acts on the nervous system is essential to scientifically validate its therapeutic effects and expand its clinical applications. Neural circuits, formed by neurons and glial cells, are the basic units responsible for transmitting and processing signals in the nervous system, controlling functions such as perception, movement, cognition, and emotion.

The study of these circuits has revealed how acupuncture can modulate different neurotransmitter systems to produce its beneficial effects.

This review study aimed to analyze the current scientific evidence on the mechanisms of the neural circuits involved in acupuncture's effects. The researchers examined studies investigating acupuncture's impact on altered neural circuits across different diseases, including pain, anxiety, Parkinson's disease, addictive disorders, cognitive impairment, and gastrointestinal disorders. The methodology involved a comprehensive review of the scientific literature, focusing on research that used modern techniques such as neural tracing, chemogenetics, optogenetics, and functional magnetic resonance imaging, combined with behavioral testing. These advanced technologies allowed researchers to precisely map the neural pathways activated by acupuncture and to observe specific changes in brain circuits before and after treatment.

The findings revealed that acupuncture exerts its therapeutic effects through modulation of specific neural circuits that vary according to the condition being treated. In pain management, acupuncture activates multiple levels of the pain control system, from sensitization of acupuncture points to activation of the descending pain inhibition system. The technique stimulates the release of endogenous opioid peptides and activates structures such as the periaqueductal gray and nucleus raphe magnus, which are fundamental for natural pain control. In addition, acupuncture modulates circuits connecting the anterior cingulate cortex, thalamus, and limbic system areas, explaining its effects on both pain and the anxiety frequently associated with chronic pain.

For Parkinson's disease, acupuncture has shown the capacity to activate brain regions affected by the disease, including the substantia nigra, striatum, and prefrontal cortex, improving the balance of basal ganglia circuits and reducing the loss of dopaminergic neurons.

The clinical implications of these findings are significant for both patients and healthcare providers. For patients, these studies offer a solid scientific basis explaining how acupuncture can effectively treat their conditions, fostering greater confidence in treatment. The understanding that acupuncture acts through well-defined neurobiological mechanisms, and not merely through a placebo effect, validates its use as a legitimate complementary therapy. The results show that acupuncture can be particularly beneficial for conditions where there is dysfunction of specific neural circuits, such as chronic pain, neurodegenerative disorders, and cognitive impairment.

For healthcare providers, these findings offer more precise guidance on when and how to use acupuncture, allowing more targeted and effective treatments. The identification of specific neural circuits also opens possibilities for the development of personalized acupuncture protocols, in which the selection of points and techniques can be tailored based on the neural circuit that needs to be modulated for each specific condition.

Despite significant advances, the study also identified important limitations that must be considered. Most research on the neural circuits of acupuncture is still performed in animal models, due to the limitations of neural tracing and manipulation technologies in humans. This raises questions about the direct translation of results to clinical practice in humans. Furthermore, existing clinical studies frequently have small sample sizes and lack standardization of the acupuncture protocols used.

Another important limitation is that current research focuses predominantly on the central nervous system, with limited studies on how acupuncture affects the complete circuit from the periphery to the central nervous system and target organs. The scope of diseases studied is also limited, concentrating mainly on pain, with less research on other conditions potentially treatable by acupuncture. For the future, the researchers recommend expanding studies to include a wider variety of diseases, developing technologies that allow more detailed studies in humans, and standardizing acupuncture protocols to improve comparability between studies. It is also essential to develop larger, multicenter clinical trials to validate animal model findings in human clinical practice.