Raffai G, Cseko C, Kocsis L, Dézsi L, Monos E
Institute of Human Physiology and Clinical Experimental Research, Semmelweis University, Budapest, Hungary.
Physiol Res. 2009;58(1):57-67. doi: 10.33549/physiolres.931264. Epub 2008 Jan 17.
Microgravity or simulated microgravity induces acute and chronic cardiovascular responses, whose mechanism is pivotal for understanding of physiological adaptation and pathophysiological consequences. We investigated hemodynamic responses of conscious Wistar rats to 45? head-down tilt (HDT) for 7 days. Arterial blood pressure (BP) was recorded by telemetry. Heart rate (HR), spectral properties and the spontaneous baroreflex sensitivity (sBRS) were calculated. Head-up tilt (HUT) was applied for 2 h before and after HDT to assess the degree of any possible cardiovascular deconditioning. Horizontal control BP and HR were 112.5+/-2.8 mmHg and 344.7+/-10 bpm, respectively. HDT elicited an elevation in BP and HR by 8.3 % and 8.8 %, respectively, in less than 1 h. These elevations in BP and HR were maintained for 2 and 3 days, respectively, and then normalized. Heart rate variability was unchanged, while sBRS was permanently reduced from the beginning of HDT (1.01+/-0.08 vs. 0.74+/-0.05 ms/mmHg). HUT tests before and after HDT resulted in BP elevations (6.9 vs. 11.6 %) and sBRS reduction (0.44 vs. 0.37 ms/mmHg), respectively. The pressor response during the post-HDT HUT test was accompanied by tachycardia (13.7 %). In conclusion, chronic HDT does not lead to symptoms of cardiovascular deconditioning. However the depressed sBRS and tachycardic response seen during the post-HDT HUT test may indicate disturbances in cardiovascular control.
微重力或模拟微重力会引发急性和慢性心血管反应，其机制对于理解生理适应和病理生理后果至关重要。我们研究了清醒的Wistar大鼠在45°头低位倾斜（HDT）7天期间的血流动力学反应。通过遥测记录动脉血压（BP）。计算心率（HR）、频谱特性和自发性压力反射敏感性（sBRS）。在HDT前后进行2小时的头高位倾斜（HUT），以评估任何可能的心血管失健程度。水平对照时的BP和HR分别为112.5±2.8 mmHg和344.7±10次/分钟。HDT在不到1小时内分别使BP和HR升高了8.3%和8.8%。这些BP和HR的升高分别维持了2天和3天，然后恢复正常。心率变异性未改变，而sBRS从HDT开始就永久性降低（1.01±0.08对0.74±0.05 ms/mmHg）。HDT前后的HUT测试分别导致BP升高（6.9%对11.6%）和sBRS降低（0.44对0.37 ms/mmHg）。HDT后HUT测试期间的升压反应伴有心动过速（13.7%）。总之，慢性HDT不会导致心血管失健症状。然而，HDT后HUT测试期间出现的sBRS降低和心动过速反应可能表明心血管控制存在紊乱。
