Effect of electroacupuncture on activation of satellite glial cells and P2X7 receptor in the DRG of rats with chronic inflammatory pain
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1.Department of Neurobiology and Acupuncture Research, the Third Clinical Medical College, Zhejiang Chinese Medical University, Key Laboratory of Acupuncture and Neurology of Zhejiang Province, Hangzhou 310053, China. 2. Department of Acupuncture and Moxibustion,the Third Affiliated Hospital of Zhejiang Chinese Medical University, Hangzhou 310005

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    Abstract:

    Objective To observe the effects of electroacupuncture (EA) on ipsilateral paw withdrawal thresholds (PWTs), activation of satellite glial cells, and the P2X7 receptor in the dorsal root ganglia (DRG) of rats with chronic inflammatory pain, and further explore the peripheral mechanism of EA against chronic inflammatory pain. Methods Part 1: Rats were randomly divided into the control group (Con group; n = 12), CFA-induced inflammatory pain group (CFA group; n = 12), CFA model plus EA treatment group (CFA + EA group; n = 12), and CFA model plus sham EA treatment group (CFA + sEA group; n = 12). The CFA inflammatory pain model was established by injecting 0. 1 mL CFA into the plantar of the rat right hind foot. EA at a 2 / 100 Hz alternative frequency and gradual intensity (0. 5, 1, and 1. 5 mA, 10 min each) was administered at acupoints “Zusanli” and “Kunlun” for 30 min per day for 7 days. PWTs were detected at 1, 3, 7, 8, 10, 12, and 14 days after CFA injection. Protein expression of glial fibrillary acidic protein (GFAP) and P2X7 receptor in DRG at day 14 post-CFA was measured by western blotting. Part 2: CFA rats were randomly divided into the CFA plus DMSO group (CFA + DMSO group; n = 8), CFA plus P2X7R agonist A740003 group (CFA + A740003 group; n = 10), EA plus normal saline group (CFA + EA + NS group; n = 8), and EA plus P2X7R agonist BzATP group (CFA + EA + BzATP group; n = 12), which were intrathecally administrated with DMSO, A740003, normal saline, and BzATP respectively. PWTs were measured at pre-surgery, pre-CFA, post-CFA, and post-intrathecal injection. Results Part 1: PWTs of CFA rats were decreased significantly (P < 0. 01) and EA significantly increased PWTs (P < 0. 01). CFA injection significantly increased the expression of GFAP and P2X7 receptor in the ipsilateral L4-6 DRG of rats (P< 0. 05). EA significantly reduced the expression of GFAP and P2X7 receptor in the L4-6 DRG of rats (P < 0. 05), but sham EA had no obvious effect (P > 0. 05). Part 2: Compared with the CFA + DMSO group, intrathecal injection of P2X7 receptor antagonist A740003 significantly increased PWTs of CFA rats (P < 0. 01). PWTs in the CFA + EA + BzATP group were significantly lower than those in the CFA + EA + NS group (P < 0. 01). Conclusions Electroacupuncture alleviates chronic inflammatory pain in rats, which might be related to the reduction of satellite glial cell activation and decrease of P2X7 receptor activation in the rat DRG. Inhibition of satellite glial cell activation and a decrease of P2X7 receptor expression contribute to EA treating chronic inflammatory pain, which may be one of the peripheral mechanisms of EA analgesia.

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History
  • Received:April 27,2020
  • Revised:
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  • Online: September 15,2020
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