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Effects of Aging on Whole‐Leg α‐Adrenergic Vasoconstrictor Responsiveness in Healthy Men
Author(s) -
Dinenno Frank A,
Smith Erica G,
Kirby Brett S,
Markwald Rachel R,
Voyles Wyatt F
Publication year - 2007
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.21.5.a565-c
Subject(s) - medicine , phenylephrine , endocrinology , adrenergic , vasoconstriction , agonist , vasodilation , adrenergic receptor , femoral artery , brachial artery , receptor , blood pressure
Muscle sympathetic vasoconstrictor nerve activity increases with advancing age, but does not result in elevated forearm vasoconstrictor tone due to a selective reduction in α 1 ‐adrenergic receptor responsiveness. In contrast, the leg circulation of older adults is under greater tonic sympathetic vasoconstriction, but it is unclear whether leg α‐receptor responsiveness is altered with age. We tested the hypothesis that α‐adrenergic receptor responsiveness is not reduced in the leg circulation with age. In 12 young (24±1 yrs) and 7 healthy older men (62±2 yrs), we measured femoral blood flow (FBF; Doppler ultrasound) and calculated the vascular conductance (FVC) responses to α‐adrenergic receptor stimulation via intra‐femoral artery infusions of tyramine (evokes endogenous NE release), phenylephrine (α 1 ‐agonist), and dexmedetomidine (α 2 ‐agonist) during local blockade of β‐adrenergic receptors. At rest, femoral blood flow and vascular conductance were ~30% lower in older compared with young men. Maximal vasoconstrictor responses (%ΔFVC) to tyramine (−30±3 vs −41±3%), phenylephrine (−25±4 vs −45±5%), and dexmedetomidine (−22±4 vs −44±3%) were significantly reduced in older compared with young men (all P <0.05). We conclude that aging is associated with impaired leg α‐adrenergic receptor responsiveness at rest, and that this involves both α 1 ‐ and α 2 ‐adrenergic receptors. Supported by AG‐022337