Sylvia A L, Piantadosi C A
Brain Res. 1985 Jul 15;338(2):281-8. doi: 10.1016/0006-8993(85)90158-1.
The effect of intravenous norepinephrine (NE) administration on three O2-dependent parameters of cerebral oxygenation was studied in the parietal cortex of skull intact anesthetized rats. Reflectance spectrophotometry was used to measure in vivo changes in cortical hemoglobin saturation (Hb/HbO2), blood volume (BV), and cytochrome c oxidase (cyt. a,a3) oxidation-reduction state. The influence of arterial pressure of oxygen (paO2) on norepinephrine-induced changes in cortical microcirculatory O2 delivery and cyt. a,a3 redox state was tested under conditions of normoxia, hypoxia, and hyperoxia. Norepinephrine produced cyt. a,a3 redox changes which were independent of compensatory alterations in cortical blood volume and changes in systemic blood pressure at the tested physiological extremes. During normoxia, NE caused dose-dependent systemic pressure-related increases in the oxidation level of cyt. a,a3. Conversely, in hypoxia NE caused a reduction. Microcirculatory and cyt. a,a3 redox responses to low doses of NE during hyperoxia were similar to those obtained at high doses during normoxia. The kinetic pattern of changes in hemoglobin saturation, cyt. a,a3 redox state, and cortical blood volume during normoxia and hypoxia was consistent with direct alteration in oxygen delivery to the respiratory chain and possible modification of cerebral oxidative metabolism. Blood-brain barrier alterations and vascular smooth muscle resistance changes to NE under tested conditions of oxygenation are postulated to be responsible for the observed results.
在颅骨完整的麻醉大鼠顶叶皮质中，研究了静脉注射去甲肾上腺素（NE）对脑氧合的三个氧依赖性参数的影响。采用反射分光光度法测量皮质血红蛋白饱和度（Hb/HbO2）、血容量（BV）和细胞色素c氧化酶（cyt. a,a3）氧化还原状态的体内变化。在常氧、低氧和高氧条件下，测试了动脉血氧分压（paO2）对去甲肾上腺素诱导的皮质微循环氧输送和cyt. a,a3氧化还原状态变化的影响。去甲肾上腺素产生的cyt. a,a3氧化还原变化与皮质血容量的代偿性改变以及在所测试的生理极端情况下的全身血压变化无关。在常氧期间，NE导致cyt. a,a3氧化水平呈剂量依赖性的全身压力相关增加。相反，在低氧时NE导致降低。高氧期间低剂量NE引起的微循环和cyt. a,a3氧化还原反应与常氧期间高剂量时获得的反应相似。常氧和低氧期间血红蛋白饱和度、cyt. a,a3氧化还原状态和皮质血容量的变化动力学模式与向呼吸链的氧输送直接改变以及脑氧化代谢的可能改变一致。推测在所测试的氧合条件下血脑屏障改变和血管平滑肌对NE的阻力变化是造成观察结果的原因。
