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OBJECTIVE:   To assess the influence of blocking smooth muscle large conductance Ca(2+) -activated K+ channels and voltage-gated K+ channels on the conducted dilation to ACh and isoproterenol. MATERIALS AND METHODS:   Rat mesenteric arteries were isolated with a bifurcation, triple-cannulated, pressurized and imaged using confocal microscopy. Phenylephrine was added to the superfusate to generate tone, and agonists perfused into a sidebranch to evoke local dilation and subsequent conducted dilation into the feed artery. RESULTS:   Both ACh- and isoproterenol-stimulated local and conducted dilation with similar magnitudes of decay with distance along the feed artery (2000μm: ∼15% maximum dilation). The gap junction uncoupler carbenoxolone prevented both conducted dilation and intercellular spread of dye through gap junctions. IbTx, TEA or 4-AP, blockers of large conductance Ca(2+) -activated K+ channels and voltage-gated K+ channels, did not affect conducted dilation to either agonist. A combination of either IbTx or TEA with 4-AP markedly improved the extent of conducted dilation to both agonists (2000μm: >50% maximum dilation). The enhanced conducted dilation was reflected in the hyperpolarization to ACh (2000μm: Control, 4±1 mV, n = 3; TEA with 4-AP, 14±3mV, n=4), and was dependent on the endothelium. CONCLUSIONS:   These data show that activated BK(Ca) and K(V) -channels serve to reduce the effectiveness of conducted dilation.

Original publication

DOI

10.1111/j.1549-8719.2011.00109.x

Type

Journal article

Journal

Microcirculation

Publication Date

08/2011

Volume

18

Pages

487 - 500

Keywords

Acetylcholine, Adrenergic beta-Agonists, Animals, Gap Junctions, Isoproterenol, Male, Mesenteric Arteries, Muscle, Smooth, Vascular, Potassium Channel Blockers, Potassium Channels, Calcium-Activated, Potassium Channels, Voltage-Gated, Rats, Rats, Wistar, Vasodilation, Vasodilator Agents