Objective: To observe the effect of electroacupuncture (EA) of "Huantiao" (GB 30) and "Weizhong" (BL 40) on the mechanical pain threshold and the long-term potentiation (LTP) of the spinal dorsal horn in rats with neuropathic pain.
Methods: Thirty SD rats were randomized into control (sham-operation), model and electroacupuncture (EA) groups, with 10 cases in each. The neuropathic pain model was established by ligature and transaction of the popliteal nerve and common peroneal nerve. EA (2 Hz, 1 mA) was applied to "Huantiao" (GB 30) and "Weizhong" (BL 40) on the affected side for 30 min, once daily for 7 days. The mechanical pain threshold of the paw was detected before and after modeling and EA. LTP of C-fiber stimulation (2 mA, 0.5 ms, 100 Hz, interval 10 s, 4 strains) evoked field potentials in spinal dorsal horn (L4/L5) was recorded in rats under anesthesia.
Results: Compared with control group, the pain threshold of model group reduced significantly from the 1st day on after ligature and transaction of the nerve (P<0.01), while 14 days after EA, it elevated evidently in comparison with model group (P<0.01), suggesting an increase of the mechanical pain threshold after EA. Comparison of the variance rates of C-fiber induced LTP of the field potential among the 3 groups showed that the variance rate of EA group was significantly lower than that of model group (P<0.01). Self-comparison of EA group showed that after EA, the variance rate of LTP reduced significantly (P<0.01).
Conclusion: EA of "Huantiao" (GB 30) and "Weizhong" (BL 40) can significantly relieve neuropathic pain in rats with nerve injury, and inhibit C-fiber high-frequency-stimulation induced LTP due to central sensitization induced abnormality synaptic transmission.