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Your search keyword '"Smith, Erica G."' showing total 2 results
Start Over Author "Smith, Erica G." Topic adrenergic alpha-agonists
2 results on '"Smith, Erica G."'

1. Ageing and leg postjunctional alpha-adrenergic vasoconstrictor responsiveness in healthy men.

Author

Smith EG, Voyles WF, Kirby BS, Markwald RR, and Dinenno FA

Subjects
Adult, Aged, Aging metabolism, Blood Flow Velocity drug effects, Dexmedetomidine pharmacology, Dose-Response Relationship, Drug, Femoral Artery innervation, Femoral Artery metabolism, Humans, Laser-Doppler Flowmetry, Male, Middle Aged, Norepinephrine metabolism, Phenylephrine pharmacology, Receptors, Adrenergic, alpha-1 metabolism, Receptors, Adrenergic, alpha-2 metabolism, Reference Values, Research Design, Sympathetic Nervous System drug effects, Sympathetic Nervous System metabolism, Tyramine pharmacology, Adrenergic alpha-1 Receptor Agonists, Adrenergic alpha-2 Receptor Agonists, Adrenergic alpha-Agonists pharmacology, Aging physiology, Femoral Artery drug effects, Leg blood supply, Vasoconstriction drug effects, Vasoconstrictor Agents pharmacology
Abstract

Muscle sympathetic vasoconstrictor nerve activity increases with advancing age, but does not result in elevated forearm vasoconstrictor tone because of a selective reduction in alpha1-adrenoceptor responsiveness. In contrast, the leg circulation of older adults is under greater tonic sympathetic vasoconstriction, but it is unclear whether alpha-adrenoceptor responsiveness is altered with age. In the present study, we tested the hypothesis that postjunctional alpha-adrenergic vasoconstrictor responsiveness is reduced in the leg circulation with age. We measured femoral blood flow (Doppler ultrasound) and calculated the femoral vascular conductance (FVC) responses to alpha-adrenoceptor stimulation during local blockade of beta-adrenoceptors in 12 young (24 +/- 1 year) and seven healthy older men (62 +/- 2 year). Whole-leg vasoconstrictor responses to local intrafemoral artery infusions of tyramine (evokes noradrenaline (NA) release), phenylephrine (alpha1-agonist) and dexmedetomidine (alpha2-agonist) were assessed. Consistent with previous data, resting femoral blood flow and FVC were approximately 30% lower in older compared with young men (P < 0.05). Maximal vasoconstrictor responses to tyramine (-30 +/- 3 versus -41 +/- 3%), phenylephrine (-25 +/- 4 versus -45 +/- 5%), and dexmedetomidine (-22 +/- 4 versus -44 +/- 3%) were all significantly lower in older compared with young men (all P < 0.05). Our results indicate that human ageing is associated with a reduction in leg postjunctional alpha-adrenoceptor responsiveness to endogenous NA release, and this reduction is evident for both alpha1- and alpha2-adrenoceptors. However, given that basal leg vascular conductance is reduced with age and is primarily mediated by sympathetic vasoconstriction, impaired alpha-adrenoceptor responsiveness does not negate the ability of the sympathetic nervous system to evoke greater tonic vasoconstriction in the leg vasculature of older men.

Published
2007
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2. Ageing and leg postjunctional α-adrenergic vasoconstrictor responsiveness in healthy men

Author

Smith, Erica G, Voyles, Wyatt F, Kirby, Brett S, Markwald, Rachel R, and Dinenno, Frank A

Subjects
Adult, Male, Aging, Leg, Sympathetic Nervous System, Tyramine, Middle Aged, Femoral Artery, Norepinephrine, Phenylephrine, Receptors, Adrenergic, alpha-2, Reference Values, Vasoconstriction, Receptors, Adrenergic, alpha-1, Adrenergic alpha-2 Receptor Agonists, Humans, Vasoconstrictor Agents, Cellular, Adrenergic alpha-1 Receptor Agonists, Adrenergic alpha-Agonists, Blood Flow Velocity, Dexmedetomidine, Aged
Abstract

Muscle sympathetic vasoconstrictor nerve activity increases with advancing age, but does not result in elevated forearm vasoconstrictor tone because of a selective reduction in α1-adrenoceptor responsiveness. In contrast, the leg circulation of older adults is under greater tonic sympathetic vasoconstriction, but it is unclear whether α-adrenoceptor responsiveness is altered with age. In the present study, we tested the hypothesis that postjunctional α-adrenergic vasoconstrictor responsiveness is reduced in the leg circulation with age. We measured femoral blood flow (Doppler ultrasound) and calculated the femoral vascular conductance (FVC) responses to α-adrenoceptor stimulation during local blockade of β-adrenoceptors in 12 young (24 ± 1 year) and seven healthy older men (62 ± 2 year). Whole-leg vasoconstrictor responses to local intrafemoral artery infusions of tyramine (evokes noradrenaline (NA) release), phenylephrine (α1-agonist) and dexmedetomidine (α2-agonist) were assessed. Consistent with previous data, resting femoral blood flow and FVC were ∼30% lower in older compared with young men (P < 0.05). Maximal vasoconstrictor responses to tyramine (−30 ± 3 versus−41 ± 3%), phenylephrine (−25 ± 4 versus−45 ± 5%), and dexmedetomidine (−22 ± 4 versus−44 ± 3%) were all significantly lower in older compared with young men (all P < 0.05). Our results indicate that human ageing is associated with a reduction in leg postjunctional α-adrenoceptor responsiveness to endogenous NA release, and this reduction is evident for both α1- and α2-adrenoceptors. However, given that basal leg vascular conductance is reduced with age and is primarily mediated by sympathetic vasoconstriction, impaired α-adrenoceptor responsiveness does not negate the ability of the sympathetic nervous system to evoke greater tonic vasoconstriction in the leg vasculature of older men.

Published
2007

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