Interaction between conducted vasodilation and sympathetic nerve activation in arterioles of hamster striated muscle
Kurjiaka, D.T.; Segal, S.S.
Circulation Research 76(5): 885-891
1995
ISSN/ISBN: 0009-7330 PMID: 7729006 Document Number: 445847
We tested the hypothesis that sympathetic nerve activity can influence the conduction of vasodilation along the arteriolar wall. Arterioles in the superfused cremaster muscle of anesthetized male hamsters (n = 21, 109 +- 4 g) were studied. Microelectrodes were positioned adjacent to the distal end of primary arterioles to stimulate sympathetic nerves throughout arteriolar networks (perivascular nerve stimulation (PNS)). Microiontophoresis micropipettes (tip outer diameter, 1 to 2 mu-m) filled with acetylcholine (ACh, 1 mol/L) were positioned adjacent to the wall of second-order (2A) or third-order (3A) arterioles apprxeq 1 mm distal to their origin to induce local and conducted vasodilation; diameter responses were recorded at the micropipette tip and at vessel origins, respectively. For 2A and 3A arterioles (resting diameters, 15 to 54 and 9 to 30 mu-m, respectively), vasoconstriction with PNS was frequency dependent (0.5 to 32 Hz); this was attenuated by 65% (P lt .05) with a-adrenoceptor blockade (phentolamine, 1 mu-mol/L). Conducted vasodilation was attenuated by gt 40% during 16-Hz PNS (P lt .05); this effect was reversed by phentolamine. In a reciprocal fashion, conducted vasodilation diminished PNS-induced vasoconstriction by apprxeq 50% (P lt .05). Elevating oxygen (from 0% to 10%) in the superfusion solution induced vasoconstriction similar to that with 16-Hz PNS yet had no effect on conduction. Neural blockade with tetrodotoxin (1 mu-mol/L) eliminated PNS-induced vasoconstriction and enhanced (P lt .05) conducted vasodilation. These findings indicate that perivascular nerves in striated muscle can influence cell-to-cell communication along the arteriolar wall both at rest and during enhanced sympathetic activity. The attenuation of sympathetic vasoconstriction by conducted vasodilation suggests a novel explanation for functional sympatholysis.