[Effects of electroacupuncture at different acupoints on the pain behavior and NMDA receptor 2 B subunit mRNA and protein expression and phosphorylation level in the cervical spinal cord in rats with thyroid regional pain].

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).

CONCLUSION

Both 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.