title: Limb-specific differences in the skin vascular responsiveness to adrenergic agonists.
abstract: In this study, to test the hypothesis that adrenergic vasoconstrictor responses of the legs are greater compared with the arms in human skin, cutaneous vascular conductance (CVC) in the forearm and calf were compared during the infusion of adrenergic agonists in healthy young volunteers. Under normothermic conditions, norepinephrine (NE, α- and β-agonist, 1 × 10(-8) to 1 × 10(-2) M), phenylephrine (PHE, α(1)-agonist, 1 × 10(-8) to 1 × 10(-2) M), dexmedetomidine (DEX, α(2)-agonist, 1 × 10(-9) to 1 × 10(-4) M), and isoproterenol (ISO, β-agonist, 1 × 10(-8) to 1 × 10(-3) M) were administered by intradermal microdialysis. Skin blood flow (SkBF) was measured by laser-Doppler flowmetry, and the local temperature at SkBF-measuring sites was maintained at 34°C throughout the experiments. CVC was calculated as the ratio of SkBF to blood pressure and expressed relative to the baseline value before drug infusion. The dose of NE at the onset of vasoconstriction and the effective dose (ED(50)) resulting in 50% of the maximal vasoconstrictor response for NE were lower (P < 0.001) in the calf than forearm. The ED(50) for PHE and DEX was also lower (P < 0.05) in the calf than forearm. Increases in CVC in response to ISO were potentially smaller in the calf, but the statistical differences in the responses were dependent on the expressions of CVC. These findings suggest that the cutaneous vasoconstrictor responsiveness to exogenous NE is greater in the legs than in the arms due to a higher α(1)- and α(2)-adrenoceptor reactivity, while the β-adrenoceptor function plays a minor role in regional differences in adrenergic vasoconstriction in normothermic humans.
authors.affiliation: Laboratory for Human Physiology, School of Health Sciences, University of Occupational and Environmental Health (UOEH) 1-1 Iseigaoka, Yahatanishi-ku, 807-8555 Kitakyushu, Japan. yamazaki@health.uoeh-u.ac.jp
authors.forename: Fumio
authors.initials: F
authors.lastname: Yamazaki
authors.forename: Nagisa
authors.initials: N
authors.lastname: Yuge
mesh_terms: D000279:Administration, Cutaneous; D058646:Adrenergic alpha-1 Receptor Agonists / Q000008:administration & dosage / Q000494:pharmacology*; D058647:Adrenergic alpha-2 Receptor Agonists / Q000008:administration & dosage / Q000494:pharmacology*; D000318:Adrenergic beta-Agonists / Q000008:administration & dosage / Q000494:pharmacology*; D000704:Analysis of Variance; D001794:Blood Pressure / Q000187:drug effects; D020927:Dexmedetomidine / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005260:Female; D006801:Humans; D007545:Isoproterenol / Q000494:pharmacology; D017078:Laser-Doppler Flowmetry; D035002:Lower Extremity; D008297:Male; D017551:Microdialysis; D017711:Nonlinear Dynamics; D009638:Norepinephrine / Q000494:pharmacology; D010656:Phenylephrine / Q000494:pharmacology; D012039:Regional Blood Flow / Q000187:drug effects; D012044:Regression Analysis; D012867:Skin / Q000098:blood supply*; D012881:Skin Temperature; D013997:Time Factors; D034941:Upper Extremity; D018924:Vascular Capacitance / Q000187:drug effects; D014661:Vasoconstriction / Q000187:drug effects*; D014662:Vasoconstrictor Agents / Q000008:administration & dosage / Q000494:pharmacology*; D055815:Young Adult
chemical_list: D058646:Adrenergic alpha-1 Receptor Agonists; D058647:Adrenergic alpha-2 Receptor Agonists; D000318:Adrenergic beta-Agonists; D014662:Vasoconstrictor Agents; D010656:Phenylephrine; D020927:Dexmedetomidine; D007545:Isoproterenol; D009638:Norepinephrine