A drug that opposes the excitatory effects of norepinephrine released from sympathetic nerve endings at alpha receptors and that causes vasodilation and a decrease in blood pressure.

• 阿尔法神经阻断剂一种药物，可以抵制交感神经末梢在阿尔法受体释放出的正肾上腺素的兴奋性效果，并引起血管舒张和血压下降