Bühler F R, Bolli P, Amann W F, Erne P, Kiowski W
J Cardiovasc Pharmacol. 1984;6 Suppl 5:S753-6. doi: 10.1097/00005344-198400065-00005.
In patients with essential hypertension, the vasodilator response in the forearm circulation to postjunctional alpha 1-adrenoceptor blockade with prazosin is enhanced. Besides the effects at classical postjunctional alpha 1-adrenoceptor, postjunctional alpha 2-adrenoceptor-mediated effects contribute to vascular tone, and these may be comparable in magnitude to those observed with prazosin. Owing to the extrajunctional localization of alpha 2-adrenoceptors, they may be preferential targets for circulating catecholamines and adrenaline in particular. No evidence of autoinhibitory noradrenaline feedback system via prejunctional alpha 2-adrenoceptors was found by measuring noradrenaline release from the forearm. Therefore increased sympathetic nerve activity, as demonstrated by increased plasma adrenaline concentrations, plays an important role in the pathophysiology of essential hypertension by contributing to increased vascular resistance. Central prejunctional alpha 2-adrenoceptor-stimulating drugs lower sympathetic nerve activity and thereby peripheral resistance and blood pressure, and this effect seems to override peripheral (pre-) and postjunctional alpha 2-adrenoceptor-stimulating effects.
在原发性高血压患者中，前臂循环对哌唑嗪所致的节后α1-肾上腺素能受体阻滞的血管舒张反应增强。除了经典节后α1-肾上腺素能受体的作用外，节后α2-肾上腺素能受体介导的效应也有助于血管张力的调节，其作用程度可能与哌唑嗪所观察到的效应相当。由于α2-肾上腺素能受体位于接头外，它们可能是循环儿茶酚胺尤其是肾上腺素的优先作用靶点。通过测量前臂去甲肾上腺素释放，未发现经由节前α2-肾上腺素能受体的自身抑制性去甲肾上腺素反馈系统的证据。因此，如血浆肾上腺素浓度升高所表明的，交感神经活动增强通过导致血管阻力增加在原发性高血压的病理生理学中起重要作用。中枢性节前α2-肾上腺素能受体激动药物可降低交感神经活动，从而降低外周阻力和血压，且这种效应似乎超过外周（前）和节后α2-肾上腺素能受体激动效应。
