丘脑中央下核内的阿片受体在介导大鼠电针镇痛中的作用

Role of opioid receptor in nucleus submedius in mediating electroacupuncture analgesia in rats

目的:观察丘脑中央下核(Sm)内的阿片受体是否参与介导电针(EA)的镇痛作用.方法:以辐射热诱发甩尾(TF)反射的潜伏期(TFL)作为伤害性反应指标,观察Sm内微量注射阿片受体拮抗剂纳洛酮对强(5.0 mA)、弱(0.5 mA)EA“足三里”穴(St.36)抑制大鼠TF反射的效应.结果:Sm内微量注射纳洛酮(1.0μg,0.5μL)阻断高强度EA对TF反射的抑制效应,但对低强度EA诱发的TF反射抑制无明显影响.当纳洛酮注射到Sm以外的部位时,对强、弱EA诱发TF反射的抑制均无明显影响.结论:Sm内的阿片受体参与介导强EA兴奋细传入纤维(Aδ和C类)产生的镇痛作用.

AIM： To study the role of opioid receptor in thalamie nucleus submedius （Sm） in mediating the electroacupuncture （EA） analgesia. METHODS： The latency （TFL） of tail-flick （TF） reflex was used as an index of nociceptive response. The effects of the opioid receptor antagonist naloxone （ 1.0 μg, 0.5 μL） microinjected into the Sm on the TF reflex inhibition induced by EA stimulation of the ＂zusanli point＂ （St. 36） with high （5.0 mA） - and low （0, 5 mA）-intensity were examined in the lightly anesthetized rats. RESULTS： Sm microinjection of naloxone antagonized the high-intensity EA-induced inhibition of the TF reflex, but did not influence the inhibition induced by the lowintensity EA stimulation. When naloxone was applied to the replacements with more than 0.5 mm dorsal, ventral and lateral to the Sm, the EA-induced inhibition was not influenced under either high- or low-intensity condition. CONCLUSION： The opioid receptors in Sm are involved in mediating the analgesia by high-intensity EA stimulation for exciting small afferent fibers （ Aδ and C groups）.