Thermographic study of in vivo modulation of vascular responses to phenylephrine and endothelin-1 by dexamethasone in the horse

Equine Veterinary Journal
C J CornelisseF J Derksen

Abstract

In vitro, glucocorticoids potentiate vasoconstriction of equine digital vessels to catecholamines and this has been implicated as a mechanism of glucocorticoid-induced laminitis. This observation has never been confirmed in vivo. To study the effects of glucocorticoid therapy on vasoconstrictor responsiveness in the horse in vivo. In a blinded, randomised cross-over experiment, 9 horses were treated with either dexamethasone (0.1 mg/kg bwt i.v. q. 24 h) or saline i.v. for 6 days. The changes in local average skin temperature before (baseline) and after intradermal injections of the alpha1-adrenoceptor agonist phenylephrine (PHE; 10(-4), 10(-5), 10(-6), 10(-7) and 10(-8) mol/l), endothelin-1 (ET-1; 10(-5), 10(-6), 10(-7), 10(-8) and 10(-9) mol/l) or ET-1 plus a blocker (BQ-123 10(-6) mol/l; RES-701 10(-6) mol/l; and L-NAME 10(-4) mol/l) were investigated with a thermograph. Dexamethasone (DEX) decreased baseline skin temperatures, suggesting reduced blood flow as a consequence of an increase in vasomotor tone. This was accompanied by potentiation of the response to PHE as demonstrated by a left shift in the dose-response curve and a decrease in the EC50. Dexamethasone did not potentiate ET-1, but the interplay with the lower bas...Continue Reading

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Citations

Jan 19, 2007·Equine Veterinary Journal·S R Bailey, J Elliott
Sep 15, 2009·Journal of Veterinary Internal Medicine·N E RobinsonF J Derksen
Jul 4, 2007·American Journal of Veterinary Research·Heather A TileyL Jill McCutcheon
Oct 25, 2017·Stem Cells Translational Medicine·Jamie A TextorDori L Borjesson
Mar 17, 2020·Journal of Equine Veterinary Science·Timothy J BrunnerSandra D Taylor
Jun 5, 2021·Journal of Veterinary Internal Medicine·Sophie Mainguy-Seers, Jean-Pierre Lavoie

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