Abstract
We previously showed that electroacupuncture (EA) activates medulla-spinal serotonin-containing neurons. The present study investigated the effects of intrathecal 5,7-dihydroxytryptamine creatinine sulfate, a selective neurotoxin for serotonergic terminals, the 5-hydroxytryptamine 1A receptor (5-HT1AR) antagonist NAN-190 hydrobromide and the 5-HT2C receptor (5-HT2CR) antagonist SB-242,084 on EA anti-hyperalgesia. EA was given twice at acupoint GB30 after complete Freund’s adjuvant (CFA) injection into hind paw. CFA-induced hyperalgesia was measured by assessing hind paw withdrawal latency (PWL) to a noxious thermal stimulus 30 min post-EA. Serotonin depletion and the 5-HT1AR antagonist blocked EA anti-hyperalgesia; the 5-HT2CR antagonist did not. Immunohistochemical staining showed that spinal 5-HT1AR was expressed and that 5-HT2CR was absent in naive and CFA-injected animals 2.5 h post-CFA. These results show a correlation between EA anti-hyperalgesia and receptor expression. Collectively, the data show that EA activates supraspinal serotonin neurons to release 5-HT, which acts on spinal 5-HT1AR to inhibit hyperalgesia.
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Acknowledgments
This work was supported by NIH Grant R21AT004113 and P01 AT002605. We would like to thank Dr. Lyn Lowry for her editorial support.
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Zhang, Y., Li, A., Xin, J. et al. Involvement of Spinal Serotonin Receptors in Electroacupuncture Anti-Hyperalgesia in an Inflammatory Pain Rat Model. Neurochem Res 36, 1785–1792 (2011). https://doi.org/10.1007/s11064-011-0495-1
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DOI: https://doi.org/10.1007/s11064-011-0495-1