Objective To observe the effect of electroacupuncture(EA)of different acupoint groups on the expression of NR 2 B subunit of N-methyl-D-aspartate(NMDA)receptor in the cervical spinal cord in rats with thyroid regional pain so as to analyze the analgesic mechanism of acupuncture for performing thyroid surgery.Methods A total of 50 Wistar rats were randomized into control

model

EA-Futu(ST 32)

EA-Hegu(LI 4)-Neiguan(PC 6

EA-LI 4-PC 6)

EA-Zusanli(ST 36)-Yanglingquan(GB 34

EA-ST 36-GB 34)groups

with 10 cases in each.Thyroid regional pain model was established by subcutaneous injection of 2.5% formaldehyde.Ten minutes after modeling

EA(2 Hz/100 Hz

1 mA)was applied to ST 32

LI 4-PC 6 and ST 36-GB 34 for 30 min respectively.The animals' face-grooming(FG)times and paw withdrawal latency(PWL)of radiant heat irradiation were recorded.The spinal cord tissues of the cervical 1-3 segments were removed for detecting the expression of NR 2 B mRNA and protein of NMDA receptor with reversed transcription-polymerase chain reaction and Western blotting techniques separately.Results After subcutaneous injection of 2.5% formaldehyde

the animals' FG times increased considerably and the PWL was shortened obviously(P<0.05).Compared with model group

the FG times of EA-ST 32 and EA-LI 4-PC 6 groups at 40-45 min and 70-75 min after modeling decreased significantly

and their PWL prolonged markedly(P<0.05).The effect of EA-ST 32 was apparently superior to that of EA-LI 4-PC 6 group in reducing FG times.No significant differences were found between EA-ST 32 and EA-LI 4-PC 6 groups in PWL

and between model and EA-ST 36-GB 34 groups(P>0.05).Results of NR 2 B mRNA and protein detections showed no significant differences among the 5 groups in their expression(P>0.05).Comparison of the phosphorylated NR 2 B among 5 groups showed that EA-ST 32 and EA-LI 4-PC 6 could effectively down-regulate 2.5% formaldehyde induced increase of NR 2 B phosphorylation levels(P<0.05)

while EA-ST 36-GB 34 had no obvious effect on it(P>0.05).ConclusionBoth EA-ST 32 and EA-LI 4-PC 6 can significantly suppress thyroid regional pain induced behavior reactions

which may be closely associated with their effects in down-regulating NR 2 B phosphorylated level.The analgesic effect of EA-ST 32 and EA-LI 4-PC 6 for thyroid surgery is relatively more effective in comparison with EA-ST 36-GB 34.