The contribution of brain angiotensin II to the baroreflex regulation of renal sympathetic nerve activity in conscious normotensive and hypertensive rats
The contribution of brain angiotensin II to the baroreflex regulation of renal sympathetic nerve activity in conscious normotensive and hypertensive rats
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DOI：
10.1113/jphysiol.2006.107326
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发表时间：
2006-07-15
影响因子：
5.5
通讯作者：
Johns, Edward J.
中科院分区：
文献类型：
--
作者：
Huang, Chunlong;Yoshimoto, Misa;Johns, Edward J.
当饮食盐摄入量增加或处于高血压状态时，脑中血管紧张素II受体密度升高。本研究的目的是评估是否血管紧张素II的压力感受器控制肾交感神经活动的调制在这些条件下改变。Wistar大鼠，喂养一个普通的（0.25% w/w钠）或高盐饮食（3.1% w/w钠），或中风倾向的自发性高血压大鼠（SHRSP）的颈动脉，颈静脉和脑室植入套管和记录电极的肾交感神经。三天后，在脑室内（i. c. v.）给予氯沙坦（15 μ g）以阻断血管紧张素AT 1受体。喂食常规饮食的大鼠平均血压为116 +/- 3 mmHg，心率为467 +/- 25次/分（-1），在静脉注射氯沙坦后保持不变。氯沙坦治疗后，肾交感神经活动压力感受器曲线的敏感性或曲率系数增加36%（P < 0.05）。在喂食高盐饮食的大鼠中，所有心血管变量和氯沙坦诱导的肾交感神经活动压力感受器曲率系数增加（29%）与常规钠饮食大鼠的值相似。心率压力感受器曲率系数在喂食常规或高盐饮食的大鼠中没有改变。SHRSPs的肾交感神经活动压力感受性反射增益曲线的斜率较小，氯沙坦给药后的增幅（54%）大于Wistar大鼠。这些数据表明，在清醒状态下，紧张性抑制作用的脑血管紧张素II的压力反射调节肾交感神经活动的不受饮食钠的提高，但其作用增强的SHRSPs。
Angiotensin II receptor density in the brain is elevated when dietary salt intake is raised or in the state of hypertension. The aim of this study was to evaluate whether the angiotensin II modulation of the baroreceptor control of renal sympathetic nerve activity was altered under these conditions. Wistar rats, fed either a regular (0.25% w/w sodium) or high-salt diet (3.1% w/w sodium), or stroke-prone spontaneously hypertensive rats (SHRSPs) were implanted with cannulae in the carotid artery, jugular vein and the cerebroventricle and with recording electrodes on the renal sympathetic nerves. Three days later, baroreceptor gain curves were generated for renal sympathetic nerve activity and heart rate before and following intracerebroventricular (i.c.v.) administration of losartan (15 mu g) to block angiotensin AT1 receptors. The rats fed a regular diet had a mean blood pressure of 116 +/- 3 mmHg and heart rate of 467 +/- 25 beats min(-1), which remained unchanged after the i.c.v. administration of losartan. The sensitivity or curvature coefficient of the baroreceptor curve for renal sympathetic nerve activity was increased by 36% (P < 0.05) following losartan. In the rats fed a high-salt diet, all cardiovascular variables and the losartan-induced increase in the baroreceptor curvature coefficient for renal sympathetic nerve activity (29%) were similar to values in rats on the regular sodium diet. The heart rate baroreceptor curvature coefficient was not altered in either the rats fed a regular or a high-salt diet. The slope of the renal sympathetic nerve activity baroreflex gain curve in the SHRSPs was less and the increase following administration of losartan (54%) was greater than in the Wistar rats. These data indicate that in the conscious state, the tonic inhibitory action of brain angiotensin II on the baroreflex regulation of renal sympathetic nerve activity was unaffected by raised dietary sodium, but its role was enhanced in the SHRSPs.