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Regional activation of rapid onset vasodilatation in mouse skeletal muscle: regulation through α‐adrenoreceptors
Author(s) -
Moore Alex W.,
Bearden Shawn E.,
Segal Steven S.
Publication year - 2010
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.2010.193672
Subject(s) - arteriole , vasodilation , vasoconstriction , phentolamine , anatomy , medicine , skeletal muscle , endocrinology , microcirculation , chemistry , stimulation
Exercise onset entails motor unit recruitment and the initiation of vasodilatation. Dilatation can ascend the arteriolar network to encompass proximal feed arteries but is opposed by sympathetic nerve activity, which promotes vasoconstriction and inhibits ascending vasodilatation through activating α‐adrenoreceptors. Whereas contractile activity can antagonize sympathetic vasoconstriction, more subtle aspects of this interaction remain to be defined. We tested the hypothesis that constitutive activation of α‐adrenoreceptors governs blood flow distribution within individual muscles. The mouse gluteus maximus muscle (GM) consists of Inferior and Superior regions. Each muscle region is supplied by its own motor nerve and feed artery with an anastomotic arteriole (resting diameter ∼25 μm) that spans both muscle regions. In anaesthetized male C57BL/6J mice (3–5 months old), the GM was exposed and superfused with physiological saline solution (35°C; pH 7.4). Stimulating the inferior gluteal motor nerve (0.1 ms pulse, 100 Hz for 500 ms) evoked a brief tetanic contraction and produced rapid (<1 s) onset vasodilatation (ROV; diameter change, 10 ± 1 μm) of the anastomotic arteriole along the active (Inferior) muscle region but not along the inactive (Superior) region ( n = 8). In contrast, microiontophoresis of acetylcholine (1 μm micropipette tip, 1 μA, 500 ms) initiated dilatation that travelled along the anastomotic arteriole from the Inferior into the Superior muscle region (diameter change, 5 ± 2 μm). Topical phentolamine (1 μ m ) had no effect on resting diameter but this inhibition of α‐adrenoreceptors enabled ROV to spread along the anastomotic arteriole into the inactive muscle region (dilatation, 7 ± 1 μm; P < 0.05), where remote dilatation to acetylcholine then doubled ( P < 0.05). These findings indicate that constitutive activation of α‐adrenoreceptors in skeletal muscle can restrict the spread of dilatation within microvascular resistance networks and thereby increase blood flow to active muscle regions.