Alpha1-Adrenergic Receptor Function and Stability in 1st versus 3rd Order Mesenteric Arteries and Veins of Normal Male Sprague Dawley Rats

Vascular branching facilitates blood flow changes and maintains cardiovascular homeostasis. Vasomotor tone is partly maintained by sympathetic nerves, ensuring moment-to-moment adjustments of net vascular tone. Norepinephrine (NE), phenylephrine and, sympathetic neurogenic mediated contractility was evaluated in 1st and 3rd order rat mesenteric small arteries (MA) and small veins (MV), exploring relative contributions from α-adrenergic receptors (α-AR). α1-AR subtype expression was quantified following NE exposure, focusing on microRNA-30c activity. The results suggested that MV are more sensitive to AR activation than MA; α1-ARs predominantly regulate AR-mediated contractility, with functional evidence of α2-AR activity in 1st order MA and 3rd order MV; NE reduces α1-AR mRNA expression in MV, possibly related to venous relaxation at high agonist concentration, but does not involve miRNA-30c activity; furthermore receptor isoform expression differs between 1st and 3rd order MA. This represents another level of regulation for branched vascular beds, enabling more precise control over vascular tone.