Cardiovascular Effects of Hind-limb Unweighing in Mice.
10.4097/kjae.2007.53.2.222
- Author:
Young Bok LEE
1
;
Jong Taek PARK
;
Hyun Kyo LIM
;
Jae Chan CHOI
;
Soon Yul KIM
;
Jun Hyun CHO
;
Kwang Ho LEE
Author Information
1. Department of Anesthesiology and Pain Medicine, Yonsei University Wonju College of Medicine, Wonju, Korea. khl6006@yahoo.co.kr
- Publication Type:Original Article
- Keywords:
baroreflex;
hind-limb unweighing;
microgravity;
orthostatic intolerance
- MeSH:
Aged;
Animals;
Arterial Pressure;
Baroreflex;
Calcium;
Carotid Arteries;
Catheters;
Heart Rate;
Humans;
Isoproterenol;
Mice*;
Muscle Cells;
Orthostatic Intolerance;
Pressoreceptors;
Sarcomeres;
Weightlessness
- From:Korean Journal of Anesthesiology
2007;53(2):222-228
- CountryRepublic of Korea
- Language:Korean
-
Abstract:
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 beta-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.
