Related Experiment Videos
Normalization of aortic function during arousal episodes in the hibernating ground squirrel
Robert H Henning1, Leo E Deelman, Roelof A Hut
1Groningen University Institute for Drug Exploration, Department of Clinical Pharmacology, Faculty of Medical Sciences, The Netherlands. R.H.Henning@med.rug.nl
Life Sciences
|August 1, 2002
Summary
Hibernating animals preserve vascular function during cooling and rewarming. Their aortic tissue shows increased contractility during torpor, which normalizes upon arousal with enhanced nitric oxide (NO) synthesis.
Area of Science:
- Physiology
- Comparative Biology
- Vascular Biology
Background:
- Hypothermia is used for organ preservation but offers incomplete protection against reperfusion injury.
- Impaired vascular properties, especially endothelium-dependent vasodilation, contribute to organ damage after rewarming.
- Hibernating animals naturally experience cycles of cooling and rewarming, suggesting inherent protective mechanisms.
Purpose of the Study:
- To investigate if hibernating animals possess mechanisms to preserve vascular function during and after cooling/rewarming cycles.
- To assess vascular adaptations in European ground squirrels during different stages of hibernation (torpor and arousal).
- To determine the role of nitric oxide (NO) in preserving vascular function throughout hibernation.
Main Methods:
- Vascular contractility of aortic tissue was measured in hibernating European ground squirrels after 24 hours and 7 days of torpor, 1.5 hours of arousal, and in non-hibernating controls.
- Experiments were conducted with and without the nitric oxide (NO) synthesis inhibitor, L-NMMA.
- Concentration-response curves for vasoconstrictors (phenylephrine, angiotensin II, KCl) and relaxation responses to acetylcholine (ACh) and sodium nitrite were analyzed.
Main Results:
- Aortic tissue from 7-day torpid squirrels exhibited doubled maximum contraction to vasoconstrictors compared to other groups.
- Maximum contraction to KCl was also doubled in 7-day torpid animals versus arousal and non-hibernating groups.
- Nitric oxide (NO) played a differential role in agonist-mediated relaxation across hibernation stages, with increased basal NO synthesis observed during arousal.
Conclusions:
- Vascular adaptations occur during hibernation (torpor).
- Increased aortic contractility during prolonged torpor returns to normal rapidly upon arousal, linked to enhanced basal NO synthesis.
- Hibernating animals have evolved effective strategies to maintain vascular function despite cycles of cooling and rewarming.