Rand M J, Yang C, Cole-Goodwin H M, McCulloch M W, Story D F
J Cardiovasc Pharmacol. 1982;4 Suppl 1:S41-5. doi: 10.1097/00005344-198200041-00009.
The effects of alpha-adrenoceptor blocking drugs on circulating catecholamines or neurogenically released noradrenaline will depend on their relative selectivity for prejunctional or postjunctional alpha-adrenoceptors. Relatively selective prejunctional alpha-adrenoceptor antagonists will block the inhibitory feedback mechanism at sympathetic nerve terminals, thus increasing transmitter release, which will tend to overcome any postjunctional alpha-adrenoceptor blockade, and responses to sympathetic nerve stimulation will be resistant to blockade. They will have noradrenolytic activity in doses which are not sympatholytic; they may even enhance sympathetic nerve activity. In contrast, selective postjunctional alpha-adrenoceptor blocking drugs will be noradrenolytic and sympatholytic. Prazosin has weak prejunctional alpha-adrenoceptors blocking activity, but is relatively selective for postjunctional alpha-adrenoceptors. Yohimbine is relatively selective for prejunctional alpha-adrenoceptors, and phentolamine is not highly selective. Selectivity for postjunctional alpha-adrenoceptors appears to be a desirable action for an antihypertensive drug of this type.
α-肾上腺素受体阻断药对循环中的儿茶酚胺或神经源性释放的去甲肾上腺素的作用，将取决于它们对突触前或突触后α-肾上腺素受体的相对选择性。相对选择性的突触前α-肾上腺素受体拮抗剂会阻断交感神经末梢的抑制性反馈机制，从而增加递质释放，这往往会克服任何突触后α-肾上腺素受体阻断作用，并且对交感神经刺激的反应将对阻断具有抗性。它们在非抗交感神经的剂量下具有去甲肾上腺素溶解活性；它们甚至可能增强交感神经活性。相比之下，选择性突触后α-肾上腺素受体阻断药将具有去甲肾上腺素溶解和抗交感神经作用。哌唑嗪具有较弱的突触前α-肾上腺素受体阻断活性，但对突触后α-肾上腺素受体具有相对选择性。育亨宾对突触前α-肾上腺素受体具有相对选择性，而酚妥拉明的选择性不高。对于这类抗高血压药物来说，对突触后α-肾上腺素受体的选择性似乎是一种理想的作用。
