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KMID : 0356920070530020222
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Korean Journal of Anesthesiology
2007 Volume.53 No. 2 p.222 ~ p.228
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Cardiovascular Effects of Hind-limb Unweighing in Mice
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Lee Yeong-Bok
Choi Jae-Chan
Kim Soon-Yul
Lee Kwang-Ho
Lim Hyun-Kyo
Park Jong-Taek
Cho Jun-Hyun
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Abstract
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Background: Orthostatic intolerance is a debilitating problem that can occur after prolonged bed-rest, exposure to microgravity, and in the elderly. This study examined the integrated cardiovascular response to baroreceptor activation in a hind-limb unweighing (HLU) mouse model of microgravity to test the hypothesis that both the pressor and contractility response are attenuated in HLU mice.
Methods: C57BL/6 mice (25-30 g body wt, 8-10 wk old) were exposed to HLU for 2 weeks. A bilateral carotid artery occlusion and open-loop baroreceptor stimulus was performed to measure the myocardial contractile responses using a left ventricular micromanometer-conductance catheter in the mice. In isolated myocytes simultaneous sarcomere shortening and calcium transient were measured in response to increasing concentrations of the ?-agonist isoproterenol.
Results: In the controls, bilateral carotid artery occlusion increased the heart rate and mean arterial pressure. These responses were markedly attenuated in the HLU mice. A bilateral carotid artery occlusion also increased the slope of the end-systolic pressure volume relationship (Ees) by 70 ± 11% and the slope was markedly attenuated to 10 ± 8% in the HLU mice. Isoproterenol increased the sarcomere shortening in both control and HLU mice in a dose-dependent manner. However the contractile response to isoproterenol was significantly attenuated in the HLU mice than the controls.
Conclusions: Both the pressor and myocardial contractile responses appear to be impaired in a mouse model of microgravity
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KEYWORD
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baroreflex, hind-limb unweighing, microgravity, orthostatic intolerance
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