In situ analysis of alpha-adrenoceptors on arteriolar and venular smooth muscle in rat skeletal muscle microcirculation.

• DOI: 10.1161/01.res.62.1.37
• Publication Date: 2012-06-12T00:17:09Z
• Authors: J E Faber
• Keywords: Phenylephrine; Alpha-2 adrenergic receptor; Methoxamine; Rauwolscine; Arteriole

The purpose of this study was to determine whether both alpha 1- and 2-adrenergic receptors exist on vascular smooth muscle microvessels adrenergic constriction anatomically distinct microvascular segments is differentially subserved by either receptor subtype. cremaster skeletal anesthetized rats acutely denervated suspended in a Krebs bath containing cocaine, normetanephrine, propranolol block uptake1, uptake2, beta-receptors, respectively. Intravital microscopy used large distributing arterioles (mean diameter, 100 microns), small precapillary (25 capacitance venules (140 microns). Concentration-response (diameter change) curves were obtained for bath-added agonists norepinephrine (mixed 1/alpha 2), phenylephrine (alpha 1), B-HT 933 2) the absence or presence antagonists prazosin 1) yohimbine 2). Apparent pD2(-log ED50) values were, respectively, as follows: (7.41 7.15), (5.95 5.41), (5.05 5.06). Low concentrations (10(-8) M) (10(-7) produced subtype-selective antagonism parallel, dextral displacement venules. arteriole pKB (-log KB) 7.83 +/- 0.65 7.36 0.46 yohimbine. Higher 3 X 10(-7) (10(-6) further but nonparallel curves. In contrast, only inhibited small, arterioles; had no effect at concentrations. These data suggest that regulation uses 2-adrenoceptors. Precapillary arterioles, however, may be predominantly 2-receptors.