Distinct roles of ASIC3 and TRPV1 receptors in electroacupuncture-induced segmental and systemic analgesia

Abstract

Previous studies have demonstrated the effects of different afferent fibers on electroacupuncture (EA)-induced analgesia. However, contributions of functional receptors expressed on afferent fibers to the EA analgesia remain unclear. This study investigates the roles of acid-sensing ion channel 3 (ASIC3) and transient receptor potential vanilloid 1 (TRPV1) receptors in EA-induced segmental and systemic analgesia. Effects of EA at acupoint ST36 with different intensities on the C-fiber reflex and mechanical and thermal pain thresholds were measured among the ASIC3^−/−, TRPV1^−/−, and C57BL/6 mice. Compared with C57BL/6 mice, the ipsilateral inhibition of EA with 0.8 C-fiber threshold (0.8Tc) intensity on C-fiber reflex was markedly reduced in ASIC3^−/− mice, whereas the bilateral inhibition of 1.0 and 2.0Tc EA was significantly decreased in TRPV1^−/− mice. The segmental increase in pain thresholds induced by 0.3 mA EA was significantly reduced in ASIC3^−/− mice, whereas the systemic enhancement of 1.0 mA EA was markedly decreased in TRPV1^−/− mice. Thus, segmental analgesia of EA with lower intensity is partially mediated by ASIC3 receptor on Aβ-fiber, whereas systemic analgesia induced by EA with higher intensity is more likely induced by TRPV1 receptor on Ad- and C-fibers.

Keywords

electroacupuncture / analgesia / ASIC3 / TRPV1 / C-fiber reflex

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Acknowledgements

This work was supported by National Natural Science Foundation of China (Nos. 81330087 and 81503668) and Beijing Natural Science Foundation (No. 7132148).

Compliance with ethics guidelines

Juanjuan Xin, Yangshuai Su, Zhaokun Yang, Wei He, Hong Shi, Xiaoyu Wang, Ling Hu, Xiaochun Yu, Xianghong Jing, and Bing Zhu declare that they have no conflict of interest. All institutional and national guidelines for the care and use of laboratory animals were followed.

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2016 Higher Education Press and Springer-Verlag Berlin Heidelberg