Alabaster V A, Solca A M
Clin Sci (Lond). 1985;68 Suppl 10:73s-75s. doi: 10.1042/cs068s073.
The effect of nifedipine on pressor dose-response curves to phenylephrine, alpha-methylnoradrenaline and angiotensin II was determined in anaesthetized cats pretreated with propranolol and atropine. The selectivity of phenylephrine and alpha-methylnoradrenaline for postjunctional alpha 1- and alpha 2-adrenoceptors respectively was demonstrated by using the selective alpha 1-adrenoceptor antagonist doxazosin and the relatively selective alpha 2-adrenoceptor antagonist rauwolscine. Nifedipine infused intravenously produced a degree of inhibition of rises in diastolic blood pressure similar to that induced by all three agonists. It is concluded that alpha 1- and alpha 2-adrenoceptor activation induced by phenylethanolamine derivatives is equally dependent on extracellular calcium for vascular smooth muscle contraction. Antagonism of sympathetically mediated or angiotensin-induced vasoconstriction could contribute to the vasodilator effects of nifedipine.
在预先用普萘洛尔和阿托品处理过的麻醉猫中，测定硝苯地平对去氧肾上腺素、α-甲基去甲肾上腺素和血管紧张素II升压剂量-反应曲线的影响。通过使用选择性α1-肾上腺素能受体拮抗剂多沙唑嗪和相对选择性α2-肾上腺素能受体拮抗剂萝芙木碱，分别证实了去氧肾上腺素和α-甲基去甲肾上腺素对节后α1-和α2-肾上腺素能受体的选择性。静脉注射硝苯地平产生的舒张压升高抑制程度与所有三种激动剂诱导的相似。得出的结论是，苯乙醇胺衍生物诱导的α1-和α2-肾上腺素能受体激活在血管平滑肌收缩方面同样依赖细胞外钙。交感神经介导或血管紧张素诱导的血管收缩的拮抗作用可能有助于硝苯地平的血管舒张作用。
