Duckles S P
Neurobiol Aging. 1983 Summer;4(2):151-6. doi: 10.1016/0197-4580(83)90040-4.
The adrenergic control of vascular smooth muscle was compared in young and adult rabbits using a variety of in vitro techniques. Norepinephrine (NE) content and accumulation of 3H-NE were not different in blood vessels from the two age groups. In contrast, stimulation-evoked release of endogenous NE was reduced by 40-60% in vessels from the aged animals. Functional studies of smooth muscle contractions were carried out using isolated ring segments of the ear artery. There were no differences in the resting force-response relationship between vessels from young and adult rabbits. Maximum contractile responses to nerve stimulation, NE or KCl were not different in vessels from the two age groups, nor was the NE ED50. However, blockade of the neuronal uptake system with desmethylimipramine produced a greater shift in the NE concentration-response curve in vessels from the young animals compared to the shift in vessels from adult animals. This observation reflects a decline in neuronal NE uptake with age. Although maximal contractile responses to transmural nerve stimulation at 16 Hz were unchanged, responses to stimulation at lower frequencies were reduced in vessels from adult rabbits, an effect which was also enhanced when an antagonist of neuronal uptake was present. Thus, there is a decline in function of adrenergic nerves in adult animals, reflected in a decrease in stimulation-evoked NE release and a decrease in norepinephrine uptake revealed by functional studies. These two effects tend to balance each other, so that there is a small decrease in contractile response to adrenergic nerve stimulation which is exacerbated when neuronal uptake mechanisms are blocked.
利用多种体外技术，对幼年和成年兔血管平滑肌的肾上腺素能控制进行了比较。两个年龄组血管中的去甲肾上腺素（NE）含量和³H-NE的积累没有差异。相比之下，老年动物血管中内源性NE的刺激诱发释放减少了40%-60%。使用耳动脉分离环段进行平滑肌收缩的功能研究。幼年和成年兔血管的静息力-反应关系没有差异。两个年龄组血管对神经刺激、NE或KCl的最大收缩反应没有差异，NE的半数有效剂量（ED50）也没有差异。然而，与成年动物血管相比，用去甲丙咪嗪阻断神经元摄取系统后，幼年动物血管中NE浓度-反应曲线的偏移更大。这一观察结果反映了随着年龄增长神经元NE摄取的下降。尽管16Hz时对跨壁神经刺激的最大收缩反应没有变化，但成年兔血管对较低频率刺激的反应降低，当存在神经元摄取拮抗剂时，这种效应也会增强。因此，成年动物肾上腺素能神经功能下降，表现为刺激诱发的NE释放减少以及功能研究显示的去甲肾上腺素摄取减少。这两种效应趋于相互平衡，因此对肾上腺素能神经刺激的收缩反应略有下降，当神经元摄取机制被阻断时这种下降会加剧。
