Increasing transmural pressure can alter the functional role of post-junctional receptor subtypes. Under conditions of changing transmural pressure, we investigated the relative contributions of alpha adrenergic (α-ARs) and endothelinergic receptors to norepinephrine (NE) and
endothelin (ET-1) contractile responses, respectively, in third-order rat mesenteric small veins (MSV) and arteries (MSA). NE, phenylephrine (PE), clonidine, and ET-1 concentration–response curves were constructed in the absence and presence of α-adrenergic and ET-1 receptor antagonists,
respectively. MSV were more sensitive to NE, PE, and ET-1 compared with MSA. The sensitivity of MSV to NE was higher than that to PE. Phentolamine (α1-AR/α2-AR antagonist) and prazosin (α1-AR antagonist) completely abolished NE responses.
Yohimbine (α2-AR antagonist) reduced NE and clonidine contractile responses in MSV. Clonidine contractile responses were reduced by prazosin in MSA. In MSA and MSV, BQ-610 (ETA receptor antagonist) but not BQ-788 (ETB receptor antagonist) reduced ET-1
contractile responses. Combined application of BQ-610 and BQ-788 caused further reduction in ET-1 concentration–response curves obtained in MSV. These results suggest that in addition to α1-ARs and ETA receptors, α2-ARs and ETB
receptors also mediate NE and ET-1 contractile responses in MSV, respectively, with no change in the participation of these receptors as transmural pressure is increased.
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alpha adrenergic receptors;
mesenteric small arteries;
mesenteric small veins;
myographie à pression;
petites artères mésentériques;
petites veines mésentériques;
Document Type: Research Article
Department of Biomedical Sciences, Ontario Veterinary College, University of Guelph, Guelph, ON N1G 2W1, Canada.
Department of Clinical Studies, Ontario Veterinary College, University of Guelph, Guelph, ON N1G 2W1, Canada.
Publication date: January 1, 2013
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