OBJECTIVETo observe the impacts of electroacupuncture (EA) on microgliacytes and astrocytes of cervical spinal cord in rats with thyroid incisional pain and explore the mechanism of acupuncture anesthesia in thyroid surgery.

METHODSSixty Wistar male rats were randomized into a normal group, a model group, a Futu (LI 18) group, a Hegu (LI 4)-Neiguan (PC 6) group and a Zusanli (ST 36)-Yanglingquan (GB 34) group, 12 rats in each one. Except the normal group, a longitudinal incision, about 1.5 cm in length was done along the neck midline in the rats of the rest groups to prepare the model of thyroid incisional pain. In the Futu (LI 18) group, the Hegu (LI 4)-Neiguan (PC 6) group and the Zusanli (ST 36)-Yanglingquan (GB 34) group, after modeling for 4 h, 24 h and 48 h, EA was applied to bilateral "Futu" (LI 18), "Hegu" (LI 4) "Neiguan" (PC 6) and"Zusanli" (ST 36) "Yanglingquan" (GB 34) separately, once a day, continuously for 3 days. In the normal group and the model group, no any intervention was applied. The thermal radiant apparatus was used to detect the thermal pain threshold (PT). The fluorescence quantitative RT-PCR and the Western blotting (WB) were used to determine the expressions of protein and gene of microglia activation markers Iba1 and CD11b and the astrocyte specific protein marker, glial fibrillary acid protein (GFAP) in cervical spinal cord (Cto C) after intervention in the rats of each group.

RESULTSAfter intervention, as compared with the normal group, in the model group, the neck PT was reduced apparently (<0.05), the expressions of Iba1 and CD11b and GFAP mRNA as well as the protein expressions in the spinal cord of Cto Cwere up-regulated apparently (<0.05,<0.01). As compared with the model group, in the Futu (LI 18) and the Hegu (LI 4)-Neiguan (PC 6) group, PT was increased significantly (both<0.05) and that did not change apparently in the Zusanli (ST 36)-Yanglingquan (GB 34) group (>0.05). In the Futu (LI 18) group, the protein and gene expressions of Iba1, CD11b and GFAP were lower than those in the model group (all<0.05). In the Hegu (LI 4)-Neiguan (PC 6) group, the expressions of Iba1 mRNA, CD11b protein, GFAP mRNA and protein were all lower apparently than those in the model group (all<0.05). In the Zusanli (ST 36)-Yanglingquan (GB 34) group, the expressions of Iba1, CD11b and GFAP proteins were not different significantly as compared with the model group (all>0.05). In the Zusanli (ST 36)-Yanglingquan (GB 34) group, the expressions of Iba1 mRNA and CD11b mRNA and protein expressions in the spinal cord of Cto Cwere higher apparently than those in the Futu (LI 18) group (<0.01,<0.05); the expressions of Iba1 mRNA and CD11b protein expressions were higher than those in the Hegu (LI 4)-Neiguan (PC 6) group (all<0.05); GFAP mRNA and protein expressions were higher apparently than those in the Futu (LI 18) group and the Hegu (LI 4)-Neiguan (PC 6) group (all<0.05).

CONCLUSIONSEA at "Futu" (LI 18) or "Hegu" (LI 4), "Neiguan" (PC 6) relieves the acute neck incisional pain in the rats and its effect may be closely relevant with the down-regulation of the activities of microgliacytes and astrocytes in the spinal cords.