Journal article
Impaired modulation of postjunctional α1‐ but not α2‐adrenergic vasoconstriction in contracting forearm muscle of postmenopausal women
The Journal of physiology, Vol.596(13), pp.2507-2519
07/01/2018
DOI: 10.1113/JP275777
PMCID: PMC6023827
PMID: 29708589
Abstract
Key points
Contraction‐mediated blunting of postjunctional α‐adrenergic vasoconstriction (functional sympatholysis) is attenuated in skeletal muscle of ageing males, brought on by altered postjunctional α1‐ and α2‐adrenergic receptor sensitivity. The extent to which postjunctional α‐adrenergic vasoconstriction occurs in the forearms at rest and during exercise in postmenopausal women remains unknown.
The novel findings indicate that contraction‐mediated blunting of α1‐ (via intra‐arterial infusion of phenylephrine) but not α2‐adrenergic (via intra‐arterial infusion of dexmedetomidine) vasoconstriction was attenuated in postmenopausal women compared to young women.
Additional important findings revealed that postjunctional α‐adrenergic vasoconstrictor responsiveness at rest does not appear to be affected by age in women.
Collectively, these results contribute to our understanding of local neurovascular control at rest and during exercise with age in women.
Contraction‐mediated blunting of postjunctional α‐adrenergic vasoconstriction (functional sympatholysis) is attenuated in older males; however, direct confirmation of this effect remains unknown in postmenopausal women (PMW). The present study examined whether PMW exhibit augmented postjunctional α‐adrenergic receptor vasoconstriction at rest and during forearm exercise compared to young women (YW). Eight YW (24 ± 1 years) and eight PMW (65 ± 1 years) completed a series of randomized experimental trials: (1) at rest, (2) under high flow (adenosine infusion) conditions and (3) during 6 min of forearm exercise at relative (20% of maximum) and absolute (7 kg) intensities. Phenylephrine (α1‐agonist) or dexmedetomidine (α2‐agonist) was administered during the last 3 min of each trial to elicit α‐adrenergic vasoconstriction. Forearm vascular conductance (FVC) was calculated from blood flow and blood pressure. Vasoconstrictor responsiveness was identified as the change in FVC (%) during α‐adrenergic agonist infusions from baseline (resting trial) or from steady‐state conditions (high flow and exercise trials). During resting and high flow trials, the %FVC during α1‐ and α2‐agonist stimulation was similar between YW and PMW. During exercise, α1‐mediated vasoconstriction was blunted in YW vs. PMW at relative (−6 ± 2% vs. −15 ± 3%) and absolute (−4 ± 2% vs. −14 ± 5%) workloads, such that blood flow and FVC were lower in PMW (P < 0.05 for all). Conversely, α2‐mediated vasoconstriction was similar between YW and PMW at relative (−22 ± 3% vs. −22 ± 4%; P > 0.05) and absolute (−19 ± 3% vs. ‐18 ± 4%; P > 0.05) workloads. Collectively, these findings demonstrate that despite similar α‐adrenergic vasoconstrictor responsiveness at rest, PMW have a decreased ability to attenuate α1‐adrenergic vasoconstriction in contracting skeletal muscle.
Key points
Contraction‐mediated blunting of postjunctional α‐adrenergic vasoconstriction (functional sympatholysis) is attenuated in skeletal muscle of ageing males, brought on by altered postjunctional α1‐ and α2‐adrenergic receptor sensitivity. The extent to which postjunctional α‐adrenergic vasoconstriction occurs in the forearms at rest and during exercise in postmenopausal women remains unknown.
The novel findings indicate that contraction‐mediated blunting of α1‐ (via intra‐arterial infusion of phenylephrine) but not α2‐adrenergic (via intra‐arterial infusion of dexmedetomidine) vasoconstriction was attenuated in postmenopausal women compared to young women.
Additional important findings revealed that postjunctional α‐adrenergic vasoconstrictor responsiveness at rest does not appear to be affected by age in women.
Collectively, these results contribute to our understanding of local neurovascular control at rest and during exercise with age in women.
Details
- Title: Subtitle
- Impaired modulation of postjunctional α1‐ but not α2‐adrenergic vasoconstriction in contracting forearm muscle of postmenopausal women
- Creators
- Nicholas T Kruse - University of IowaWilliam E Hughes - University of IowaKenichi Ueda - University of IowaSatoshi Hanada - University of IowaAndrew J Feider - University of IowaErika Iwamoto - University of IowaJoshua M Bock - University of IowaDarren P Casey - University of Iowa
- Resource Type
- Journal article
- Publication Details
- The Journal of physiology, Vol.596(13), pp.2507-2519
- DOI
- 10.1113/JP275777
- PMID
- 29708589
- PMCID
- PMC6023827
- ISSN
- 0022-3751
- eISSN
- 1469-7793
- Number of pages
- 13
- Grant note
- National Heart, Lung, and Blood Institute Research (HL‐105467; T32HL‐007121)
- Language
- English
- Date published
- 07/01/2018
- Academic Unit
- Anesthesia; Physical Therapy and Rehabilitation Science; Fraternal Order of Eagles Diabetes Research Center; Internal Medicine
- Record Identifier
- 9984007163202771
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