Kiang J G, Wei E T
Regul Pept. 1983 Jul;6(3):255-62. doi: 10.1016/0167-0115(83)90144-1.
Intravenous injection of opioid agonists in rats evokes a vagal reflex resulting in a fall in heart rate, and blood pressure. Three opioid antagonists, naloxone, SMS 201-995, and ICI 154,129 were used to assess the nature of the opioid receptors that mediate the vagal reflex. The agonists used were morphine, Tyr-Pro-NMePhe-D-Pro-NH2 (PLO17), and D-Ala2-Leu5-enkephalin (DADL). At challenge doses of morphine, PLO17, and DADL at five times the ED50 for bradycardia, the naloxone ED50 for DADL was nine times greater than that for morphine and PLO17. The pA2 value of naloxone against DADL was significantly less than that for morphine and PLO17. The antagonist properties of SMS 201-995 were similar to those of naloxone. ICI 154,129, a putative delta receptor antagonist, was not, however, selective in its antagonism of opioid bradycardia. Both SMS 201-995 and ICI 154,129, when injected alone, produced changes in heart rate and blood pressure. The cardiovascular actions of the peptide antagonists were not affected by naloxone hydrochloride at doses up to 4 mg/kg i.v.
给大鼠静脉注射阿片类激动剂会引发迷走神经反射，导致心率和血压下降。使用三种阿片类拮抗剂纳洛酮、SMS 201-995和ICI 154,129来评估介导迷走神经反射的阿片受体的性质。所使用的激动剂为吗啡、酪氨酰-脯氨酰-去甲苯丙氨酰-右旋脯氨酰胺（PLO17）和D-丙氨酸2-亮氨酸5-脑啡肽（DADL）。在以心动过缓的ED50的五倍剂量给予吗啡、PLO17和DADL进行激发试验时，DADL的纳洛酮ED50比吗啡和PLO17的大九倍。纳洛酮对DADL的pA2值显著低于对吗啡和PLO17的pA2值。SMS 201-995的拮抗特性与纳洛酮相似。然而，推定的δ受体拮抗剂ICI 154,129在拮抗阿片类心动过缓方面并无选择性。单独注射SMS 201-995和ICI 154,129时，均会引起心率和血压的变化。肽类拮抗剂的心血管作用不受静脉注射高达4 mg/kg剂量的盐酸纳洛酮的影响。
