Wallenstein M C
Eur J Pharmacol. 1979 Nov 16;59(3-4):253-60. doi: 10.1016/0014-2999(79)90288-7.
Morphine has been reported to both lower blood pressure (BP) and cause excitation in some species. These are seemingly contradictory effects. In this series of experiments, the actions of morphine on BP, heart rate (HR) and pupillary diameter were re-examined in sedated, paralyzed cats under 2 ranges of dosage and 3 types of sedative. Small doses (1--2 mg/kg) lowered BP and HR while larger doses (8--12 mg/kg) increased both BP and HR. The effect of morphine on pupillary diameter, however, was not biphasic in that increasing doses proportionally increased pupillary diameter. In adrenalectomized cats smaller doses of morphine decreased, but larger doses no longer increased, BP and HR as it has in the non-adrenalectomized animals. Morphine also no longer produced mydriasis in the adrenalectomized cats. The results suggest that, in the cat, morphine can have a biphasic effect and that the adrenals may play a role in the excitatory phase.
据报道，吗啡在某些物种中既能降低血压（BP）又能引起兴奋。这些作用看似相互矛盾。在这一系列实验中，在两种剂量范围和三种镇静剂类型下，对镇静、麻痹的猫重新研究了吗啡对血压、心率（HR）和瞳孔直径的作用。小剂量（1 - 2毫克/千克）可降低血压和心率，而大剂量（8 - 12毫克/千克）则会使血压和心率均升高。然而，吗啡对瞳孔直径的影响并非呈双相性，即随着剂量增加，瞳孔直径成比例增大。在肾上腺切除的猫中，较小剂量的吗啡会降低血压和心率，但较大剂量不再像在未切除肾上腺的动物中那样使其升高。吗啡在肾上腺切除的猫中也不再产生散瞳作用。结果表明，在猫中，吗啡可产生双相作用，且肾上腺可能在兴奋期发挥作用。
