RESUMEN
OBJECTIVE: To observe the effect of electroacupuncture (EA) of local plus distal acupoints on spinal substance P expression in chronic radicular pain (CRP) rats so as to investigate its underlying mechanism in the treatment of chronic radical pain. METHODS: Twenty-five Wistar rats were randomized into control, model, local acupoints [LA, bilateral "Jiaji" (EX-B 2)], distal acupoints [DA, bilateral "Yanglingquan" (GB 34)], and LA+ DA groups, with 5 cases in each. CRP model was duplicated by implanting a gel-silicon wrapping the nerve root of L4 under anesthesia. EA (2 Hz, < or =2 mA) was applied to EX-B2 and GB34 for 30 min for 8 days. Pathological changes of the local focus tissue were observed by HE dyeing, and the animals' motor state was also observed. The pain threshold was detected by using tail-flick method. Substance P immunoreactive (IR) positive product of the spinal dorsal horn (L3-L5) was detected by immunohistochemical method and expressed as integrated optical density (IOD). RESULTS: The motor scores on day 35 after modeling and pain threshold values on day 4 and 8 after treatment in EX-B2 group, GB34 group and EX-B2 + GB34 group were significantly higher than those in model group (P < 0.05, 0.01). Compared with model group, IOD values of SP in the spinal dorsal horn in EX-B2 , GB34 and EX-B2 + GB34 groups were significantly lower (P < 0.05). There were no significant differences among the 3 EA groups in the expression of SP in the spinal dorsal horn. CONCLUSION: EA of EX-B2, GB34 and EX-B2 + GB34 all has a good analgesic effect in CRP rats, which may be realized partially by suppressing the release of SP in the spinal cord. No significant differences were found among local acupoint, distal acupoint and local plus distal acupoint groups in relieving CRP, improving motor and decreasing SP expression.