Baroreflex control of heart rate (HR) has been studied in normotensive (NT) and hypertensive (HT) awake and anaesthetized animals and man, but baroreflex control of sympathetic nerve activity has not been well studied. We investigated baroreflex control of HR and renal sympathetic nerve activity (RSNA) over a wide range of arterial pressure (AP) in conscious and isoflurane (ISO) anaesthetized NT and HT rabbits. 2. Animals were instrumented to record AP, HR and RSNA. Hypertension was accomplished by renal encapsulation. AP-HR and AP-RSNA baroreflex function curves were obtained while awake and after 1.0, 1.5, 2.0 and 2.5% ISO. All baroreflex curves were fit to sigmoid or exponential functions. 3. In conscious rabbits, HT for 3-5 weeks, AP was significantly higher (75.6 +/- 0.8 vs 102.3 +/- 8.9 mmHg); HR significantly lower (218.0 +/- 5.5 vs 189.5 +/- 5.5 beats/min); and RSNA not different than NT rabbits (14.9 +/- 2.2 vs 9.9 +/- 3.2% max RSNA). 4. ISO shifted AP-HR and AP-RSNA baroreflex curves to the left in NT and HT animals, and significantly attenuated baroreflex range and slope. At low ISO concentrations, baroreflex compensation for decreases in AP is limited to small increases in HR and sympathetic nerve activity. At higher ISO concentrations, baroreflex responses to decreases in AP are lost. RSNA responses to increases in AP are preserved with increasing ISO concentrations while HR responses are progressively attenuated. The sole effect of chronic hypertension was to shift the AP-HR and AP-RSNA barocurves to the right along the pressure axis in both conscious and ISO anaesthetized animals with no additional change in range or slope. 5. At this stage of hypertension development, ISO anaesthesia affects baroreflex function equally in normotensive and hypertensive rabbits.
摘要
已在清醒和麻醉状态下的正常血压（NT）及高血压（HT）动物与人身上研究了压力感受性反射对心率（HR）的控制，但对交感神经活动的压力感受性反射控制尚未得到充分研究。我们在清醒和异氟烷（ISO）麻醉的NT和HT兔中，在较宽的动脉压（AP）范围内研究了压力感受性反射对HR和肾交感神经活动（RSNA）的控制。2. 对动物进行仪器安装以记录AP、HR和RSNA。通过肾脏包裹来实现高血压。在清醒状态以及1.0%、1.5%、2.0%和2.5% ISO麻醉后，获得AP - HR和AP - RSNA压力感受性反射功能曲线。所有压力感受性反射曲线均拟合为S形或指数函数。3. 在清醒兔中，高血压持续3 - 5周后，AP显著升高（75.6±0.8 vs 102.3±8.9 mmHg）；HR显著降低（218.0±5.5 vs 189.5±5.5次/分钟）；RSNA与NT兔无差异（14.9±2.2 vs 9.9±3.2%最大RSNA）。4. ISO使NT和HT动物的AP - HR和AP - RSNA压力感受性反射曲线向左移动，并显著减弱压力感受性反射范围和斜率。在低ISO浓度时，压力感受性反射对AP降低的代偿仅限于HR和交感神经活动的小幅增加。在较高ISO浓度时，压力感受性反射对AP降低的反应丧失。随着ISO浓度增加，RSNA对AP升高的反应得以保留，而HR反应逐渐减弱。慢性高血压的唯一影响是使清醒和ISO麻醉动物的AP - HR和AP - RSNA压力感受性反射曲线沿压力轴向右移动，范围或斜率无额外变化。5. 在高血压发展的这个阶段，ISO麻醉对正常血压和高血压兔的压力感受性反射功能影响相同。
