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No effect of systemic isocapnic hypoxia on α‐adrenergic vasoconstrictor responsiveness in human skin
Author(s) -
Simmons G. H.,
Fieger S. M.,
Wong B. J.,
Minson C. T.,
Halliwill J. R.
Publication year - 2011
Publication title -
acta physiologica
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.591
H-Index - 116
eISSN - 1748-1716
pISSN - 1748-1708
DOI - 10.1111/j.1748-1716.2010.02193.x
Subject(s) - yohimbine , tyramine , hypoxia (environmental) , vasoconstriction , medicine , endocrinology , microdialysis , adrenergic , vasodilation , chemistry , anesthesia , receptor , oxygen , antagonist , central nervous system , organic chemistry
Hypoxia impairs body temperature regulation and abolishes the decline in skin temperature associated with cold exposure, suggesting that cutaneous vasoconstriction is impaired. Aim: The purpose of this study was to test the hypothesis that cutaneous vasoconstriction to intradermal tyramine, an index of post‐junctional vasoconstrictor responsiveness, is reduced during hypoxia. Methods: Twelve subjects (six males, six females) had three microdialysis fibres placed in the ventral forearm. Fibres received either lactated ringers, 5 m m yohimbine (α‐adrenergic blockade), or 10.5 μ m BIBP‐3226 (to antagonize neuropeptide Y Y 1 receptors). Skin blood flow was assessed at each site (laser‐Doppler flowmetry) and cutaneous vascular conductance (CVC) was calculated (red blood cell flux/mean arterial pressure) and scaled to baseline. Vasoconstrictor responses to tyramine (173 μ m ) were tested during normoxia and steady‐state isocapnic hypoxia (SaO 2 = 80%) in random order. Results: During normoxia, tyramine reduced CVC by 56.0 ± 5.6 and 50.3 ± 8.0% in control and BIBP‐3226 sites (both P < 0.05 vs. pre‐tyramine; P = 0.445 between sites) whereas CVC in the yohimbine site did not change ( P = 0.398 vs. pre‐tyramine). During isocapnic hypoxia, tyramine reduced CVC by 55.9 ± 5.1 and 54.2 ± 5.4% in control and BIBP‐3226 sites (both P < 0.05 vs. pre‐tyramine; P = 0.814 between sites) whereas CVC was unchanged in the yohimbine site ( P = 0.732 vs. pre‐tyramine). Isocapnic hypoxia did not affect vasoconstrictor responses at any site (all P > 0.05 vs. normoxia). Conclusion: We conclude that post‐junctional α‐adrenergic vasoconstrictor responsiveness is not affected by hypoxia in non‐acral skin.