大鼠丘脑中央下核内注射5-HT_2受体拮抗剂噻庚啶对强电针镇痛的阻断效应

Blocking effects of 5-HT_2 receptor antagonist cyproheptadine applied to thalamic nucleus submedius on analgesia produced by high intensity electroacupuncture stimulation in rats

以辐射热诱发浅麻大鼠甩尾 (TF)反射潜伏期为痛反应指标 ,观察了不同强度电针的镇痛效应及丘脑中央下核 (Sm)内微量注射 5- HT2 受体拮抗剂噻庚啶 (CPT)对其效应的影响。结果表明 ,弱电针刺激 (0 .5m A)“足三里穴”仅可轻度抑制大鼠 TF反射 ,而强电针 (5m A)对 TF反射的抑制作用明显大于弱电针 ;单侧Sm内微量注射 CPT(50 ng)可轻度易化 TF反射 ,并使强电针的镇痛效应明显减弱 ,而对弱电针的效应无明显影响。提示 Sm内的 5- HT及其受体亚型 (5- HT2 受体 )

The analgesic effects produced by high and low intensity electroacupuncture (EA) stimulation of the “Zusanli point” were examined using latency of tail flick (TF) reflex evoked by radiant heat as an index of nociceptive response in the rat lightly anesthetized with pentobarbital. The blocking effects of 5 HT 2 receptor antagonist cyproheptadine (CPT) applied unilaterally to thalamic nucleus submedium (Sm) on both analgesic effects were determined. The results showed that although either high or low intensity EA stimulation could significantly depress the TF reflex, the analgesia produced by high intensity EA (5 mA) was significantly stronger than that obtained from low intensity EA (0.5 mA). Furthermore, CPT (50 ng) microinjection unilaterally into Sm lightly facilitated the TF reflex and effectively antagonized the analgesic effects produced by high intensity EA, but did not influence that produced by low intensity EA, suggesting that the 5 HT and its receptor subtype (5 HT 2 receptor) in Sm may be involved in mediating the analgesia induced by high intensity EA, and may exert a tonic descending inhibitory influence on nociceptive responses. [