Central Reflex Effects of Hypoxia on Muscle Oxygenation
We postulated that whole body hypoxia causes O2 demand to increase in skeletal muscle because hypoxia stimulates sympathetic release of catecholamines which are calorigenic. Such an effect would be masked in a typical hypoxia model in which regional O2 uptake would also be limited by O2 availability. Our first goal in these experiments was to circumvent this difficulty and demonstrate that our postulate was correct. The second goal for these experiments was to determine the strength and duration of centrally mediated vasoconstriction in muscle in the absence of local hypoxia. Previous studies (Cain and Chapler, 1979; 1980) have shown that muscle vascular resistance increased less than 20% in severe whole body hypoxia and that after 30 min of hypoxia, local dilatory factors had overcome any vasoconstriction. To meet both these goals, we maintained normoxic regional perfusion to hindlimb skeletal muscles of anesthetized dogs by use of a pump and membrane oxygenator while ventilating the animal with an hypoxic gas mixture. To show the role of innervation in regional hypoxic reactions, we compared metabolic and hemodynamic events in innervated and denervated limbs.
KeywordsHypoxic Hypoxia Succinylcholine Chloride Global Hypoxia Calorigenic Effect Intact Innervation
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- Bredle, D.L., Chapler, C.K., and S.M. Cain, 1988a, Metabolic and circulatory responses of normoxic skeletal muscle to whole body hypoxia, J. Appl. Physiol, (in press).Google Scholar
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