The mechanistic basis for the effects of electroacupuncture on neuropathic pain within the central nervous system

Neuropathic pain is a type of chronic pain caused by injuries or diseases that affect the nervous system, significantly impacting patients' quality of life. This complex condition affects approximately 7% of the general population, accounting for 15% to 25% of all chronic pain cases. Unlike other types of pain, neuropathic pain results from alterations in the normal functioning of nerves and may manifest as burning, stabbing, or crushing sensations, often accompanied by hypersensitivity to stimuli that would not normally cause pain. The conventional treatment currently available has important limitations regarding efficacy and is frequently associated with significant side effects, creating an urgent need to explore safer and more effective alternative therapeutic approaches.

This study consisted of a comprehensive narrative review that examined the mechanisms by which electroacupuncture may relieve neuropathic pain in the central nervous system. The researchers conducted a systematic search of the PubMed database, focusing on studies published between January 2012 and January 2022. The inclusion criteria were rigorously defined to encompass only studies published in English that investigated the analgesic mechanisms of electroacupuncture and its application in the treatment of neuropathic pain, with specific focus on central mechanisms. Conference abstracts, clinical studies, systematic reviews, and meta-analyses were excluded.

At the end of the selection process, 79 relevant articles were included in the analysis, providing a solid basis for understanding the mechanisms of action of electroacupuncture in the central nervous system.

The results of the review revealed that electroacupuncture exerts its analgesic effects through multiple complex and interconnected signaling pathways in the central nervous system. The research demonstrated that low frequencies of electrical stimulation, particularly between 2 and 10 Hz, are more effective in suppressing neuropathic pain compared to higher frequencies such as 100 Hz. The identified mechanisms include modulation of the endogenous opioid system, with activation of μ, δ, and κ receptors in the spinal cord and release of β-endorphins in the brain. Electroacupuncture also significantly influences the amino acid neurotransmitter system, reducing the release of excitatory substances such as glutamate and aspartate, while promoting the release of inhibitory neurotransmitters such as GABA, glycine, and taurine.

Additionally, descending serotonergic and noradrenergic pathways are activated, contributing to inhibitory pain control. The endocannabinoid system also plays a fundamental role, particularly through CB1 receptors, modulating pain transmission both in the spinal cord and in specific brain regions.

For patients and health professionals, these findings offer encouraging perspectives on the use of electroacupuncture as a safe, non-addictive, and economically viable therapeutic approach for the management of neuropathic pain. Understanding these mechanisms allows professionals to optimize treatment protocols by appropriately selecting the most suitable acupuncture points, stimulation frequencies, and intensities for each specific case. For patients, this means access to a therapeutic option that can be incorporated into conventional treatment protocols, potentially reducing dependence on traditional analgesic medications and their associated side effects. The results also suggest that electroacupuncture may be particularly beneficial when applied at specific points such as Zusanli (ST-36), Huantiao (GB-30), and other traditionally used points, demonstrating that the precise location of acupuncture points is crucial to maximize therapeutic benefits.

However, this study has some important limitations that should be considered when interpreting the results. First, most of the analyzed research was conducted in animal models, particularly rats, which may limit the direct applicability of the findings to humans. Second, there is a significant gap in the understanding of the brain mechanisms of electroacupuncture, since most studies focused on effects at the spinal cord level. Third, much of the research focused on specific signaling pathways in isolation, without adequately exploring the complex interactions between multiple neurotransmitter systems.

Finally, the traditional theoretical basis of Chinese medicine regarding meridians and acupuncture points still lacks convincing anatomical correlation with known structures of Western medicine. Future studies should address these gaps through robust clinical research, more in-depth investigation of brain mechanisms, and exploration of interactions between different signaling pathways to provide a more complete and integrated understanding of the therapeutic effects of electroacupuncture in the treatment of neuropathic pain.