Journal
PHYSIOLOGICAL REPORTS
Volume 2, Issue 10, Pages -Publisher
WILEY
DOI: 10.14814/phy2.12164
Keywords
Exercise; nitric oxide; sympathetic nervous system; sympatholysis; vascular conductance
Categories
Funding
- Natural Sciences and Engineering Research Council of Canada (NSERC)
- Canadian Foundation for Innovation
- Alberta Advanced Education and Technology
- NSERC Canada Graduate Doctoral Scholarship
- University of Alberta Presidents' Scholarship
- Izaak Walton Killam Memorial Scholarship
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Tetrahydrobiopterin (BH4) is an essential cofactor for the production of nitric oxide (NO) and supplementation with BH4 improves NO-dependent vasodilation. NO also reduces sympathetic vasoconstrictor responsiveness in resting and contracting skeletal muscle. Thus, we hypothesized that supplementation with BH4 would blunt sympathetic vasoconstrictor responsiveness in resting and contracting skeletal muscle. Sprague-Dawley rats (n = 15, 399 +/- 57 g) were anesthetized and instrumented with an indwelling brachial artery catheter, femoral artery flow probe, and a stimulating electrode on the lumbar sympathetic chain. Triceps surae muscles were stimulated to contract rhythmically at 30% and 60% of maximal contractile force (MCF). The percentage change of femoral vascular conductance (%FVC) in response to sympathetic stimulations delivered at 2 and 5 Hz was determined at rest and during muscle contraction in control and acute BH4 supplementation (20 mg center dot kg(-1) +/- 10 mg center dot kg(-1)center dot h(-1), IA) conditions. BH4 reduced (P < 0.05) the vasoconstrictor response to sympathetic stimulation (i.e., decrease in FVC) at rest (Control: 2 Hz: -28 +/- 5%FVC; 5 Hz: -45 +/- 5%; BH4: 2 Hz: -17 +/- 4% FVC; 5 Hz: -34 +/- 7% FVC) and during muscular contraction at 30% MCF (Control: 2 Hz: -14 +/- 6% FVC; 5 Hz: -28 +/- 11%; BH4: 2 Hz: -6 +/- 6% FVC; 5 Hz: -16 +/- 10%) and 60% MCF (Control: 2 Hz: -7 +/- 3% FVC; 5 Hz: -16 +/- 6% FVC; BH4: 2 Hz: -2 +/- 3% FVC; 5 Hz: -11 +/- 6% FVC). These data are consistent with our hypothesis that acute BH4 supplementation decreases sympathetic vasoconstrictor responsiveness in resting and contracting skeletal muscle.
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