Abstract
Neuropathic pain (NeuP) is an important clinical problem accompanying negative mood symptoms. Neuroinflammation in the amygdala is critically involved in NeuP, and the dopamine (DA) system acts as an important endogenous anti-inflammatory pathway. Electroacupuncture (EA) can improve the clinical outcomes in NeuP, but the underlying mechanisms have not been fully elucidated. This study was designed to assess the effectiveness of EA on pain and pain-related depressive-like and anxiety-like behaviors and explore the role of the DA system in the effects of EA. Male Sprague-Dawley rats were subjected to the chronic constrictive injury (CCI) model to induce NeuP. EA treatment was carried out for 30 min once every other day for 3 weeks. The results showed that CCI caused mechanical hyperalgesia and depressive and anxiety-like behaviors in rats and neuroinflammation in the amygdala, such as an increased protein level of TNFα and IL-1β and activation of astrocytes. EA treatment significantly improved mechanical allodynia and the emotional dysfunction induced by CCI. The effects of EA were accompanied by markedly decreased expression of TNFα, IL-1β, and glial fibrillary acid protein (GFAP) in the amygdala. Moreover, EA treatment reversed CCI-induced down-regulation of DA concentration, tyrosine hydroxylase (TH) expression, and DRD1 and DRD2 receptors. These results suggest that EA-ameliorated NeuP may possibly be associated with the DA system to inhibit the neuroinflammation in the amygdala.
Highlights
Neuropathic pain (NeuP) is a disabling condition that is induced by peripheral and/or central nerve injury and is estimated to affect between 100 and 560 million people worldwide (Baron, 2006; Alles and Smith, 2018)
After the rats received the constrictive injury (CCI) surgery, the Mechanical withdrawal thresholds (MWT) of their ipsilateral hindpaws decreased significantly on day 7 compared with the sham group, which indicated that CCI induced a prominent mechanical allodynia
The present study demonstrated that EA treatment alleviated nociceptive and behavioral impairment associated with CCI-induced NeuP
Summary
Neuropathic pain (NeuP) is a disabling condition that is induced by peripheral and/or central nerve injury and is estimated to affect between 100 and 560 million people worldwide (Baron, 2006; Alles and Smith, 2018). NeuP is characterized by persistent and intractable pain but is associated with negative emotions, such as anxiety and depression (Khan et al, 2020). A simultaneous intervention on pain-modulating pathways and mood/affect networks is considered to be an effective treatment for NeuP (Mitsi et al, 2015). Clinical treatment is still challenging because of limited efficacy and many side effects of pharmacological therapy, and NeuP can be refractory. Many patients seek help from complementary and alternative medicine treatments, such as acupuncture
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