Campagnole-Santos M J, Heringer S B, Batista E N, Khosla M C, Santos R A
Department of Physiology and Biophysics, Federal University of Minas Gerais, Brazil.
Am J Physiol. 1992 Jul;263(1 Pt 2):R89-94. doi: 10.1152/ajpregu.1992.263.1.R89.
The present study was designed to investigate the effect of intracerebroventricular (icv) and intravenous (iv) infusion of angiotensin (ANG)-(1-7), ANG III, and ANG II on the baroreceptor control of heart rate (BHR) in conscious rats. Reflex changes in HR were elicited by bolus iv injection of either phenylephrine or sodium nitroprusside before and within 1 and 3 h of icv infusion of ANG II (n = 10), ANG III (n = 9), ANG-(1-7) (n = 9), or saline (n = 9) at a rate of 3 nmol.7.5 microliter-1.h-1. In another group of animals (n = 23), iv infusion of the same amount of ANG peptides was carried out at a rate of 0.7 ml/h. The average ratio of changes in HR in beats per minute and changes in mean arterial pressure (MAP, mmHg) was used as an index of BHR sensitivity. ANG II and ANG III produced a significant increase in the basal levels of MAP, but only during the first hour of infusion (iv or icv). No significant changes in baseline HR were observed. ANG-(1-7) and saline infusion did not change basal levels of HR or MAP (iv or icv). ANG II (iv and icv) and ANG III (icv) caused a significant decrease in the BHR sensitivity for reflex bradycardia. In contrast, icv infusion of ANG-(1-7) induced a significant increase in BHR sensitivity for reflex bradycardia (-3.0 +/- 0.3, 1 h, and -2.8 +/- 0.1 beats.min-1.mmHg-1, 3 h vs. -2.1 +/- 0.2 beats.min-1.mmHg-1, before infusion).(ABSTRACT TRUNCATED AT 250 WORDS)
本研究旨在探讨脑室内（icv）和静脉内（iv）输注血管紧张素（ANG）-(1-7)、ANG III和ANG II对清醒大鼠心率压力感受器控制（BHR）的影响。在以3 nmol·7.5微升⁻¹·小时⁻¹的速率icv输注ANG II（n = 10）、ANG III（n = 9）、ANG-(1-7)（n = 9）或生理盐水（n = 9）之前以及输注后1小时和3小时内，通过静脉推注去氧肾上腺素或硝普钠引发心率的反射性变化。在另一组动物（n = 23）中，以0.7毫升/小时的速率静脉输注相同量的ANG肽。每分钟心率变化与平均动脉压（MAP，mmHg）变化的平均比值用作BHR敏感性指标。ANG II和ANG III使MAP的基础水平显著升高，但仅在输注的第一小时（静脉或脑室内）。未观察到基线心率有显著变化。ANG-(1-7)和生理盐水输注未改变心率或MAP的基础水平（静脉或脑室内）。ANG II（静脉和脑室内）和ANG III（脑室内）导致反射性心动过缓的BHR敏感性显著降低。相反，icv输注ANG-(1-7)导致反射性心动过缓的BHR敏感性显著增加（-3.0±0.3，1小时，以及-2.8±0.1次·分钟⁻¹·mmHg⁻¹，3小时，对比输注前的-2.1±0.2次·分钟⁻¹·mmHg⁻¹）。（摘要截短于250字）
