Acute hemodynamic responses in the head during microgravity induced by free drop in anesthetized rats
Acute hemodynamic responses in the head during microgravity induced by free drop in anesthetized rats
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DOI：
10.1152/ajpregu.00653.2003
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发表时间：
2004-06-01
影响因子：
2.8
通讯作者：
Morita, H
中科院分区：
文献类型：
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作者：
Gotoh, TM;Fujiki, N;Morita, H
为了检查头部对微重力（muG）的急性To血流动力学反应，我们测量颈动脉压（CAP）和颈静脉压（JVP）以计算头部灌注压（CPP = CAP-JVP），并记录虹膜中微血管的图像以评估在由自由下落诱导的4.5s的muG期间麻醉大鼠中的毛细血管血流速度（CBFV）和毛细血管直径（CD）。将大鼠置于30 °头高位全身倾斜（HU，n = 7）或水平（平卧，n = 6）位置。在平坦组中，测量变量均未受到muG的显著影响，而在HU组中，CAP、JVP和CPP分别增加23.4 +/- 2.6、1.3 +/- 0.2和22.9 +/- 3.1 mmHg，CBFV和CD分别增加33 +/- 8和9 +/-3%，显示毛细血管血流量增加。为了进一步研究这些CAP和JVP增加的机制，进行了另一个实验，其中在麻醉大鼠（n = 6）中从HU到平躺的姿势变化期间测量CAP和JVP。在这些动物中，JVP的变化与实际muG期间观察到的变化相似，但没有观察到CAP的变化，表明实际muG期间JVP的增加是由头到脚轴的重力压力梯度消失引起的，而CAP的增加不是。总之，由于CAP的增加大于JVP的增加，实际μ G会增加CPP，导致毛细血管血流量增加。虽然JVP的增加是由muG导致的从头到脚轴的重力压力梯度的消失来解释的，但CAP的较大增加不是。
To examine acute To hemodynamic responses to microgravity (muG) in the head, we measured carotid artery pressure (CAP) and jugular vein pressure (JVP) to calculate cephalic perfusion pressure (CPP = CAP - JVP) and recorded images of microvessels in the iris to evaluate capillary blood flow velocity (CBFV) and capillary diameter (CD) in anesthetized rats during 4.5 s of muG induced by free drop. Rats were placed in 30degrees head-up whole body-tilted (HU, n = 7) or horizontal (flat, n = 6) position. In the flat group, none of the measured variables was significantly affected by muG, whereas in the HU group, CAP, JVP, and CPP increased, respectively, by 23.4 +/- 2.6, 1.3 +/- 0.2, and 22.9 +/- 3.1 mmHg, and CBFV and CD increased, respectively, by 33 +/- 8 and 9 +/- 3%, showing an increase in capillary blood flow. To further examine the mechanisms underlying these CAP and JVP increases, another experiment was performed in which CAP and JVP were measured in anesthetized rats (n = 6) during a postural change from HU to flat. In these animals, the change in JVP was similar to that observed during actual muG, but no change in CAP was seen, indicating that the JVP increase during actual muG is caused by disappearance of the gravitational pressure gradient in the head-to-foot axis, whereas the CAP increase is not. In conclusion, actual muG elicits an increase in CPP due to a greater increase in CAP than JVP, resulting in increased capillary blood flow. Although the increase in JVP is explained by the disappearance of gravitational pressure gradient in the head-to-foot axis as a result of muG, the larger increase in CAP is not.