Electroacupuncture induces antihyperalgesic effect through endothelin-B receptor in the chronic phase of a mouse model of complex regional pain syndrome type I
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Complex regional pain syndrome (CRPS) is a disorder that involves abnormal inflammation and nerve dysfunction frequently resistant to a broad range of treatments. Peripheral nerve stimulation with electroacupuncture (EA) has been widely used in different clinical conditions to control pain and inflammation; however, the use of EA in the treatment of CRPS is under investigation. In this study, we explore the effects of EA on hyperalgesia and edema induced in an animal model of chronic post-ischemia pain (CPIP model) and the possible involvement of endothelin receptor type B (ETB) in this effect. Female Swiss mice were subjected to 3 h hind paw ischemia/reperfusion CPIP model. EA treatment produced time-dependent inhibition of mechanical and cold hyperalgesia, as well as edema in CPIP mice. Peripheral administration (i.pl.) of BQ-788 (10 nmol), an ETB antagonist, prevented EA-induced antihyperalgesia while intrathecal administration prolonged EA’s effect. Additionally, peripheral pre-treatment with sarafotoxin (SRTX S6c, 30 pmol, ETB agonist) increased EA anti-hyperalgesic effect. Furthermore, the expression of peripheral ETB receptors was increased after EA treatments, as measured by western blot. These results may suggest that EA’s analgesic effect is synergic with ETB receptor activation in the periphery, as well as central (spinal cord) ETB receptor blockade. These data support the use of EA as a nonpharmacological approach for the management of CRPS-I, in an adjuvant manner to ETB receptor targeting drugs.
KeywordsChronic pain Chronic post-ischemia pain Neuropathic pain Sanyinjiao (SP6) Zusanli (ST36)
Sources of funding
The present study was supported by grants from Universidade do Sul de Santa Catarina—Curso de Medicina and Programa Unisul de Iniciação Científica (PUIC), Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES), Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq - 476454/2013-1), and Fundação de Amparo à Pesquisa e Inovação do Estado de Santa Catarina (FAPESC-3414/2012), Brazil.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
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