Stürmer E
Cardiology. 1976;61 suppl 1:290-301. doi: 10.1159/000169822.
Ergot alkaloids increase the tone of isolated canine vein strips dose-dependently in concentrations considerably lower than noradrenaline, but the maximal responses are only about one third of those to noradrenaline. This action can be blocked by prior administration of phentolamine. It is therefore concluded that the long-lasting stimulant action of ergot alkaloids on vascular smooth muscle is mediated mainly by alpha-adrenoceptors. Using the autoperfused hind limb of the cat, it has been shown that dihydroergotamine increases dose-dependently the tone of the capacitance vessels in a manner very similar to electrical stimulation of the sympathetic nerve with increasing frequencies. However, in contrast to sympathetic nerve stimulation, dihydroergotamine elicits only a very weak increase in arteriolar resistance.
麦角生物碱能以剂量依赖性方式增强离体犬静脉条的张力，其所需浓度远低于去甲肾上腺素，但最大反应仅为去甲肾上腺素的约三分之一。预先给予酚妥拉明可阻断此作用。因此可以得出结论，麦角生物碱对血管平滑肌的持久刺激作用主要由α-肾上腺素能受体介导。利用猫的自体灌注后肢已表明，双氢麦角胺能以与交感神经电刺激频率增加时非常相似的方式，剂量依赖性地增强容量血管的张力。然而，与交感神经刺激不同，双氢麦角胺仅引起小动脉阻力非常微弱的增加。
