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Effects of Phenylephrine and Norepinephrine on the Diameter of the Epineurial Vessels Supplying the Sciatic Nerve
Author(s) -
Cleary Shane R.,
Orr Julie I.,
Killey Chelsa,
Jackson Dwayne N.,
Frisbee Jefferson C.,
Twynstra Jasna
Publication year - 2018
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.2018.32.1_supplement.705.3
Subject(s) - vasoconstriction , phenylephrine , sciatic nerve , anesthesia , medicine , intravital microscopy , mean arterial pressure , norepinephrine , anatomy , blood pressure , microcirculation , heart rate , dopamine
Background Phenylephrine (PE) and norepinephrine (NE) are known vasoconstrictors; however, little is known about their role in blood flow regulation at the sciatic nerve. The purpose of this study was to determine the effects of PE and NE on the epineurial vessels supplying the sciatic nerve. Methods Adult male Sprague‐Dawley rats (323.1 ± 5.2 g) were anaesthetized using urethane, α‐chloralose, then were tracheotomized, catheterized, and had the sciatic nerve exposed. Alexa Fluor 488 Isolectin GS‐IB4 conjugate [178.6 μm/ml] was used to label the endothelial cells of the vessel wall allowing for visualization of the epineurial vessels using intravital video microscopy. PE (10 −5 M) or NE (10 −5 M) was topically applied to the sciatic region for 4 minutes, separately. Images were obtained at baseline, immediately prior to drug application, and every minute for 4 minutes during application. Data are expressed at the time point that maximum change in diameter occurred. Data are expressed as mean ± standard error. Results Application of PE (n=11) resulted in a vasoconstriction (baseline: 22.0 ± 2.1 μm, PE: 19.3 ± 2.0 μm; P<0.05). Similarly, topical application of NE (n=8) induced a vasoconstriction (baseline: 31.2 ± 4.5 μm, NE: 26.5 ± 4.6 μm; P<0.05). Mean arteriolar pressure was unaffected during either PE (baseline: 99.1 ± 5.6 mmHg, PE: 97.4 ± 5.4 mmHg) or NE (baseline: 104.0 ± 4.5 mmHg, NE: 107.3 ± 7.7 mmHg) application. Conclusion Both PE and NE caused vasoconstriction at the sciatic nerve, which is consistent with previous studies in other tissues observing vasoconstriction through activation of α‐1 adrenergic receptors. As PE and NE are both α‐1 receptor agonists, these findings suggest that α‐1 receptors may be involved in blood flow regulation at the peripheral nerves. Support or Funding Information This study was supported by the SEED Research Grant from The University of Western Ontario. This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .