Institute of Clinical Experimental Research, Semmelweis University, Budapest, Hungary.
Department of General Pharmacology, Gedeon Richter Plc., Budapest, Hungary.
Hypertens Res. 2018 Jan;41(1):18-26. doi: 10.1038/hr.2017.91. Epub 2017 Oct 26.
The frequent accompaniment of hypertension by orthostatic circulatory disorders prompted us to investigate the effect of repeated and sustained head-up and head-down tilt positions on cardiovascular responses in spontaneously hypertensive rats vs. Wistar rats using radiotelemetric implants. Repeated orthostasis caused a transient elevation in blood pressure (7.3±1.7 mmHg) and heart rate (39.7±10.5 BPM), while repeated antiorthostasis led only to reversible tachycardia (85.6±11.7-54.3±16.8 BPM) in spontaneously hypertensive rats. In contrast to the Wistar rats, sustained tilt failed to affect the blood pressure or heart rate in spontaneously hypertensive rats because the environmental stress of being placed in horizontal tilt cages prior to the sustained tilt test induced marked changes in cardiovascular parameters. Non-specific stress responses were eliminated both by the anxiolytic diazepam and a sub-anesthetic dose of chloralose. Unlike diazepam, chloralose amplified the orthostatic pressor responses in the Wistar rats. In contrast to diazepam preventing the pressor response and associated tachycardia in spontaneously hypertensive rats, chloralose elicited this effect during both sustained orthostasis (36.0±7.3 mmHg, 63.7±21.8 BPM) and antiorthostasis (42.9±10.9 mmHg, 82.8±25.4 BPM), with a reduced baroreflex sensitivity. However, during sustained orthostasis, removal of the vestibular input led to a depressor response with bradycardia (12.5±3.2 mmHg, 59.3±17.3 BPM), whereas antiorthostasis only reduced blood pressure (20.5±7.1 mmHg) in the spontaneously hypertensive rats. We conclude that repeated tilts induce a transient pressor response and/or tachycardia in spontaneously hypertensive rats. Cardiovascular parameters are suppressed by diazepam, whereas chloralose evokes both blood pressure and heart rate responses during sustained tilts, which are primarily elicited by baroreflex suppression in hypertension. Vestibular inputs support cardiovascular tolerance to sustained postural changes in a rat model of human 'essential' hypertension.
高血压常伴有直立循环障碍，这促使我们使用无线电遥测植入物研究反复和持续的头高位和头低位倾斜对自发性高血压大鼠与 Wistar 大鼠心血管反应的影响。反复直立会导致血压短暂升高（7.3±1.7mmHg）和心率加快（39.7±10.5BPM），而反复抗直立仅导致自发性高血压大鼠的心动过速可逆（85.6±11.7-54.3±16.8BPM）。与 Wistar 大鼠不同，持续倾斜对自发性高血压大鼠的血压或心率没有影响，因为在进行持续倾斜试验之前，将其置于水平倾斜笼中作为环境应激，导致心血管参数发生明显变化。在 Wistar 大鼠中，苯二氮䓬和氯醛糖的亚麻醉剂量消除了非特异性应激反应。与苯二氮䓬不同，氯醛糖放大了 Wistar 大鼠的直立升压反应。与苯二氮䓬防止自发性高血压大鼠的升压反应和相关心动过速不同，氯醛糖在持续直立（36.0±7.3mmHg，63.7±21.8BPM）和抗直立（42.9±10.9mmHg，82.8±25.4BPM）期间都引起这种效应，同时降低了压力反射敏感性。然而，在持续直立期间，去除前庭输入会导致血压下降和心动过缓（12.5±3.2mmHg，59.3±17.3BPM），而抗直立仅降低自发性高血压大鼠的血压（20.5±7.1mmHg）。我们得出结论，反复倾斜会导致自发性高血压大鼠出现短暂的升压反应和/或心动过速。苯二氮䓬抑制心血管参数，而氯醛糖在持续倾斜期间会引起血压和心率反应，这主要是由于高血压时压力反射抑制引起的。前庭输入支持大鼠模型中人类“原发性”高血压对持续姿势变化的心血管耐受。
