Effect of cooling on vascular smooth muscle from the thirteen-lined ground squirrel |
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| Authors: | C T Harker R C Webb |
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| Affiliation: | 1. Centre for Community Child Health, Murdoch Children''s Research Institute, Royal Children''s Hospital (S Guo, S Goldfeld, and N Priest), Melbourne, Australia;2. Department of Pediatrics, University of Melbourne (S Guo, M O''Connor, F Mensah, and S Goldfeld), Melbourne, Australia;3. Melbourne Children''s LifeCourse Initiative, Murdoch Children''s Research Institute (M O''Connor), Melbourne, Australia;4. Intergenerational Health, Murdoch Children''s Research Institute (F Mensah), Melbourne, Australia;5. Centre for Adolescent Health, Murdoch Children''s Research Institute, Royal Children''s Hospital (CA Olsson), Melbourne, Australia;6. Centre for Social and Early Emotional Development, School of Psychology, Faculty of Health, Deakin University (CA Olsson), Geelong, Australia;7. Research Department of Epidemiology and Public Health, University College London (RE Lacey), London, United Kingdom;8. Department of Social and Behavioral Sciences, Harvard T. H. Chan School of Public Health (N Slopen), Boston, Mass;9. National Centre for Epidemiology and Population Health, Research School of Population Health, The Australian National University (KA Thurber), Canberra, Australia;10. Centre for Social Research & Methods, The Australian National University (N Priest), Canberra, Australia;1. Dept. of Zoology, Tel-Aviv University, Tel-Aviv, Israel;2. School of Behavioral Sciences, Tel Aviv-Yaffo Academic College, Tel-Aviv, Israel;3. Dept. of Clinical Biochemistry and Pharmacology, Ben-Gurion University of the Negev, Beersheba, Israel;4. College of Pharmacy, University of Minnesota, USA;1. Department of Psychology, University of Virginia, United States of America;2. Department of Psychology, McGill University, Canada;3. Advanced Research Computing Services, University of Virginia, United States of America |
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| Abstract: | Peripheral vascular resistance in the ground squirrel (Spermophilus tridecemlineatus) increases when the animal enters hibernation. The goals of this study were to determine if a change in vascular reactivity contributes to this hemodynamic response, and to compare the effects of temperature on vascular responsiveness in a hibernator (ground squirrel) and a nonhibernating mammal (rat). Helically cut strips of aortae and femoral arteries were mounted in organ chambers (37 degrees C) and isometric contractions were recorded. The arteries were made to contract in response to exogenous norepinephrine (5.9 X 10(-7) M). Cooling the organ chamber (11 degrees C) potentiated contractions to norepinephrine (5-15% increase) in ground squirrel femoral arteries but depressed those (80-100% decrease) in ground squirrel aortae and rat aortae and femoral arteries. Contractions in response to depolarizing concentrations of potassium in ground squirrel femoral arteries were depressed by cooling (11 degrees C), suggesting that the augmented response to norepinephrine at low temperature is specific. Treatment with indomethacin, propanolol, and ouabain did not alter the potentiating effect of temperature on contractions to norepinephrine in ground squirrel femoral arteries. Apparently, the potentiation is not related to prostaglandins generated in the vascular wall, to blockade of beta-adrenergic receptors, nor to inhibition of the electrogenic sodium pump. The observations are consistent with the hypothesis that a change in vascular responsiveness contributes to the regional control of blood flow in hibernation. This adaptive response is specific in that it does not occur in the aorta of the ground squirrel and the response is not present in the vasculature of the rat, a nonhibernating mammal. |
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