Aging and Forearm Postjunctional α-Adrenergic Vasoconstriction in Healthy Men
Why the study?
Does aging reduce forearm postjunctional alpha-adrenergic responsiveness to endogenous norepinephrine release in healthy men?
Population
20 healthy normotensive men, comprising 10 young and 10 older individuals.
Comparison
Local intra-arterial infusions of tyramine… vs Comparison between young and older men.
Design
Cross-sectional
Authors
Discussion
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Implication
Supports age-related reduction in alpha-adrenergic vasoconstriction; leaves open its role in clinical vascular regulation.
Key Points
- To determine whether preserved vascular tone despite increased sympathetic nerve activity in aging is caused by reduced postjunctional alpha1- or alpha2-adrenergic responsiveness to norepinephrine.
- Studied 10 young men (aged 26±1 years) and 10 older men (aged 65±1 years), all healthy and normotensive.
- Measured forearm blood flow via strain-gauge plethysmography during intra-arterial infusions of tyramine, phenylephrine, and clonidine following beta-adrenergic blockade with propranolol.
- Quantified sympathetic alpha-adrenergic vasoconstrictor tone using nonselective alpha-receptor blockade with phentolamine.
- Maximal forearm blood flow reduction to tyramine was blunted in older versus young men (-37±3% vs -49±3%, P<0.01) despite higher deep venous norepinephrine concentration (910±103 vs 565±69 pg/mL, P<0.001).
- Vasoconstriction to selective alpha1-stimulation with phenylephrine was significantly blunted in older compared to young men (-47±2% vs -58±3%, P<0.05), whereas responses to clonidine were -36±7% versus -40±3%.
- Basal forearm sympathetic alpha-adrenergic vasoconstrictor tone revealed by phentolamine infusion was significantly lower in older men.
Structured PICO
Does aging reduce forearm postjunctional alpha-adrenergic responsiveness to endogenous norepinephrine release in healthy men?
P
Population
20 healthy normotensive men, comprising 10 young (mean age 26+/-1 years) and 10 older (mean age 65+/-1 years) individuals.
I
Intervention
Local intra-arterial infusions of tyramine, phenylephrine, and clonidine after local beta-adrenergic blockade with propranolol.
C
Comparator
Comparison between young and older men.
O
Outcome
Forearm blood flow (FBF) responses measured by strain-gauge plethysmography.surrogate
Human aging is associated with a reduction in forearm postjunctional alpha1-adrenergic responsiveness to endogenous norepinephrine release, contributing to reduced sympathetic vasoconstrictor tone.
Cite This Study
Dinenno et al. (2002) studied this question.