Gu H, Barron B A, Gaugl J F, Caffrey J L
Department of Physiology, Texas College of Osteopathic Medicine, Fort Worth 76107.
Circ Shock. 1993 Jul;40(3):206-11.
Naloxone potentiates the inotropic effect of circulating catecholamines in the isolated canine heart. The stereospecificity of this response was evaluated with the aid of the less active (+)enantiomer of naloxone. The more common (-)isomer of naloxone increased the contractile response to epinephrine only at the higher dose tested (4 mg). This effect of naloxone was not observed at a tenfold lower dose (0.4 mg), indicating a very narrow dose-response range. (+)Naloxone was effective at the lower dose and was, therefore, equal to or better than (-)naloxone in potentiating the inotropic effect of epinephrine. When introduced afterward, (-)naloxone did not add to the effect of (+)naloxone. These data suggest that naloxone modifies cellular responsiveness to catecholamines through a nontraditional opiate receptor, through a nonopiate receptor, or through a nonreceptor mechanism.
纳洛酮可增强离体犬心脏中循环儿茶酚胺的正性肌力作用。借助活性较低的纳洛酮（+）对映体评估了这种反应的立体特异性。纳洛酮较常见的（-）异构体仅在较高测试剂量（4毫克）时增加了对肾上腺素的收缩反应。在低十倍的剂量（0.4毫克）下未观察到纳洛酮的这种作用，表明剂量反应范围非常窄。（+）纳洛酮在较低剂量时有效，因此在增强肾上腺素的正性肌力作用方面等于或优于（-）纳洛酮。当随后引入（-）纳洛酮时，并未增强（+）纳洛酮的作用。这些数据表明，纳洛酮通过非传统阿片受体、非阿片受体或非受体机制改变细胞对儿茶酚胺的反应性。
