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Smooth muscle BK channels oppose sympathetic nerve‐evoked constrictions in mesenteric resistance arteries
Author(s) -
Krishnamoorthy Gayathri,
Heppner Thomas,
Nelson Mark T.
Publication year - 2009
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.23.1_supplement.611.4
Subject(s) - bk channel , mesenteric arteries , phenylephrine , chemistry , vasodilation , vasoconstriction , anatomy , potassium channel , medicine , endocrinology , blood pressure , artery
Large conductance, calcium‐ and voltage‐sensitive potassium (BK) channels have been shown to oppose constrictions to changes in intravascular pressure ("myogenic tone"). The role of BK channels in the modulation of sympathetic tone is not known. Here, we propose that smooth muscle BK channels oppose nerve‐evoked constrictions in resistance arteries of the mesenteric circulation. Sympathetic nerves on third order pressurized (60 mm Hg) arteries were stimulated by short (1s) and long (50s) electrical pulse trains. Diameter changes were recorded using edge‐detection software in the presence and absence of BK channel blockers. The blocker of BK channels, paxilline (1 μM), increased nerve‐induced constrictions by about 1.6‐fold for short and long stimulation pulses. In addition, paxilline increased the duration of the evoked constrictions (4.55 min ± 0.17 sem in control vs. 5.6 min ± 0.19 sem in paxilline). The effect of paxilline on neurotransmission was determined by measuring junctional calcium transients (jCaTs), which reflect the release of ATP from nerve varicosities. Paxilline also increased constrictions to exogenous application of phenylephrine, an α‐adrenergic agonist, by about 1.8‐fold. These results indicate that BK channels act in a negative feedback fashion to oppose nerve‐induced constrictions and regulate the sympathetic tone of resistance arteries of the mesenteric circulation. These studies highlight the importance of the BK channel in opposing sympathetic tone.