Chronic pain, especially the chronic neuropathic pain syndrome characterized by long duration, slow recovery and difficulty to control in clinic practice makes it more serious physically and psychologically. Nowadays, the field of chro nic neuropathic pain has been grasping more and more attention. The present stud y aims at investigating the optimal interval parameter of the electroacupunctur e (EA) treatment. L 5/L 6 nerve ligation model was used to assess the effect o f EA on neuropathic pain. Mechanical allodynia was assessed by 50% paw withdrawal t hreshold and cold induced ongoing pain was detected by the number of paw lifts within 5 minutes when free rat was put on to 5±1 ℃ cold plate. Han’s Acupoint Nerve Stimulator (HANS) was connected to needles inserted into acupo ints "Jiaji"(EX B 2/L 5) and "Weizhong" (BL 40) on both sides. Other parame ters were: intensity of 0.5～ 1 mA, 1～2 mA , ten minutes each; frequency of 2 H z; and 0.6 ms in pulse width. Different interval parameter was Q 1 day (one tr eatment/day), Q 2 day, Q 3 day and Q 4 day. Results: Optimal interval pla ys a critical r ole for the analgesic effect of electroacupuncture. The interval of Q 1 day ha s a declining analgesic effect or even not any effect. The other 3 groups have accumulative effect and long lasting analgesic effect (24 hours for mechanical allodynia and 1 week for cold induced ongoing pain). Compared with the control, there is a significant difference (P<0.01 or 0.001). Among these 4 in tervals, Q 3 day group is the best. Longer lasting analgesic effect following this interval choice (48 hours for mechanical allodynia and 10 days for cold i nduced ongoing pain). Amongst the 4 interval parameters, Q 3 day group has don e better effect than the others(P<0.01 or 0.001). The results indicate that one EA treatment every 3 days is the optimal interval. And it may have som ething to do with the clinical practice.
