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Simulated microgravity increases myogenic tone in rat cerebral arteries
G G Geary1, D N Krause, R E Purdy
1Department of Pharmacology, College of Medicine, University of California, Irvine, California 92697-4625, USA. gggeary@uci.edu
Journal of Applied Physiology (Bethesda, Md. : 1985)
|November 6, 1998
Summary
Simulated microgravity from hindlimb unweighting (HU) increased cerebral artery tone in rats. This effect was partly mediated by nitric oxide synthase, impacting cerebral circulation adaptation.
Area of Science:
- Neuroscience
- Cardiovascular Physiology
- Space Medicine
Background:
- Cerebral circulation adaptation to microgravity is not fully understood.
- Hindlimb unweighting (HU) in rats simulates microgravity effects.
- Cerebral arteries play a key role in regulating brain blood flow.
Purpose of the Study:
- To investigate the impact of simulated microgravity on rat middle cerebral artery myogenic responses.
- To determine the role of nitric oxide synthase in these adaptations.
Main Methods:
- Middle cerebral arteries were isolated from hindlimb unweighted (HU) and control rats.
- Myogenic responses were measured under varying transmural pressures.
- The effect of NG-nitro-L-arginine methyl ester (a nitric oxide synthase inhibitor) was assessed.
Main Results:
- Arteries from HU rats exhibited significantly smaller diameters under pressure compared to controls.
- This difference was attenuated by NG-nitro-L-arginine methyl ester, indicating a nitric oxide synthase-dependent component.
- Transient distensibility decreased, while vasomotion frequency and amplitude increased after HU, independent of nitric oxide synthase.
Conclusions:
- Simulated microgravity increases cerebral artery myogenic tone via both nitric oxide synthase-dependent and -independent pathways.
- These findings suggest complex adaptations in cerebral circulation during spaceflight.
- Understanding these mechanisms is crucial for mitigating spaceflight-induced neurological risks.