咪唑啉受体参与痛觉调制和针刺镇痛

The Role of Imidazoline Receptors in Pain Modulation and Acupuncture Analgesia

目的 :观察咪唑啉受体在痛觉调制和针刺镇痛中的作用。方法 :本文以辐射热照射致甩尾反射潜伏期作为测痛的指标 ,采用蛛网膜下腔注射 (ith)咪唑啉受体的激动剂和拮抗剂的方法观察咪唑啉受体对痛阈和针刺镇痛效应的影响。结果 :ith可乐宁和电针双侧“次”穴可产生明显的镇痛效应 ,均可被事先注射咪唑啉受体的拮抗剂苯恶唑 (Idazoxan)所阻断。结论 :说明激活咪唑啉受体可能是可乐宁和电针镇痛效应的共同脊髓机制 。

Objective: To observe the effect of spinal subarachnoid injection of clonidine and idazoxan on pain reaction and acupuncture analgesia for analyzing the action of imidazoline receptors in acupuncture analgesia. Methods: SD female rats (220±15 g) were used in the present study. The latency of tail flick in response to radiation heat stimulation was employed as the pain index. Bilateral 'Ciliao' (BL 32) wee punctured with filiform needles and stimulated electrically by setting the stimulation parameters being 1 ～2 mA (electric current), 50 Hz (frequency) and duration of 20 min. Under urethane anesthesia (1 g/kg, i.p.), an polyethylene catheter was implanted into the rat subarachnoid space of the lumbar spinal cord for microinjection of clonidine (5, 25 or 50 μg /10 μL), normal saline (NS, 10 μL ) or idazoxan (60 μg/10 μL), a selected antagonist of imidazoline receptors. Every administration of the aforementioned drugs consisted of 6 ～8 cases of rats. Results: After microinjection of clonidine (25 and 50 μg /10 μL) the pain threshold increased significantly in comparison with basal value (P< 0.05), that was blocked completely by pre administration of idazoxan (60 μg/10 μL). Following EA of 'Ciliao' (BL 32), the pain threshold also increased significantly and this effect of EA could be blocked partially by pre treatment with idazoxan (60 μg). There was a significant difference between idazoxan and NS pre treatment in influencing the analgesic effect of EA (P<0.01). Despite no significant effect of subarachnoid injection of 5 μg clonidine on pain threshold or acupuncture analgesia was found, if used together with morphine, it could apparently strengthen the analgesic effect of morphine (50 μg/10 μL), which was strikingly stronger than that of simple microinjection of morphine (P< 0.01). Conclusion: The above mentioned results suggest that activation of the spinal imidazoline receptors is involved in both clonidine antinociception and acupuncture analgesia.