SYSTEMIC ALPHA-2 ADRENORECEPTOR BLOCKADE AND HEART RATE AND FOREARM

交感神经系统和儿茶酚胺动力学的研究 可以提供对冠状动脉和全身血流调节的了解。 虽然α-肾上腺素受体阻滞剂产生血管舒张， 突触前α-2受体刺激去甲肾上腺素的释放。到 评估全身性α-2受体阻滞剂对心脏的影响， 对12例冠状动脉造影正常的患者静脉滴注育亨宾 动脉我们测量了全身和冠状动脉血流动力学， 冠状动脉血流和阻力，以及去甲肾上腺素溢出到 体动脉、冠状静脉和股静脉。育亨宾增加了 去甲肾上腺素溢出至心大静脉、动脉和股静脉 静脉分别为117，157和852%。全身α 2阻滞 心脏去甲肾上腺素溢出增加，冠状动脉无变化 血管阻力，与增加的阻力和更大的 前臂去甲肾上腺素溢出增加因此，直接 育亨宾阻断α-2的血管舒张作用被 由于释放去甲肾上腺素而产生的血管收缩作用，尤其是在 体循环

Investigation of the sympathetic nervous system and catecholamine kinetics may provide insight into coronary and systemic blood flow regulation. Although alpha-adrenoceptor blockade produces vasodilatation, blockade of presynaptic alpha-2 receptors stimulates release of norepinephrine. To assess the impact of systemic alpha-2 receptor blockade on the heart, yohimbine was infused intravenously in 12 patients with normal coronary arteries. We measured systemic and coronary hemodynamics and systemic and coronary flow and resistance, as well as norepinephrine spillover into the systemic artery and coronary and femoral veins. Yohimbine increased the spillover of norepinephrine into the great cardiac vein, artery and femoral vein by 117, 157, and 852% respectively. Systemic alpha-2 blockade increased cardiac norepinephrine spillover with no change in coronary vascular resistance, contrasting with increased resistance and much larger increases in norepinephrine spillover in the forearm. Thus, direct vasodilator effects of alpha-2 blockade by yohimbine are overwhelmed by vasoconstrictor effects due to a release of norepinephrine, especially in the systemic circulation.