Effects of Acupuncture on Neuropathic Pain: Mechanisms in Animal Models

Abstract

Neuropathic pain is a chronic condition/disease characterized by mechanical and thermal pain. Neuropathic pain can have various comorbidities such as depression, anxiety disorders and cognitive impairment, and as a result, can have a detrimental effect on quality of life. Pain and comorbid symptoms are often complicated, intertwined, affect each other, and present difficulties in treatment. Therefore, it is necessary to improve both pain and comorbid symptoms to treat neuropathic pain. Acupuncture is effective in treating not only pain but other conditions/diseases such as depression, anxiety, and cognitive impairment. Recently, acupuncture was reported to be effective in improving comorbid symptoms in patients with chronic pain. This review aimed to describe the mechanisms of action of acupuncture on the brain with respect to the improvement of comorbid symptoms that appeared in animal models of chronic neuropathic pain. Comorbidity-pain studies were comprehensively reviewed. Both manual acupuncture and electroacupuncture improved not only mechanical and thermal pain but also comorbid symptoms such as depression, anxiety, and cognitive impairment in patients with chronic neuropathic pain. The results of this review suggest that comorbid symptoms can be improved through various mechanisms, including the dopamine system in the brain, glutamate system, inflammation, epigenetic modulation, and mitochondrial function.