Intermediate-conductance calcium-activated potassium channels participate in neurovascular coupling
| Autor: | T A, Longden, K M, Dunn, H J, Draheim, M T, Nelson, A H, Weston, G, Edwards |
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| Rok vydání: | 2011 |
| Předmět: |
Male
Patch-Clamp Techniques Small-Conductance Calcium-Activated Potassium Channels Brain Endothelial Cells Mice Transgenic Intermediate-Conductance Calcium-Activated Potassium Channels Immunohistochemistry Membrane Potentials Mice Inbred C57BL Vasodilation Arterioles Mice HEK293 Cells Astrocytes Potassium Channel Blockers Animals Humans Calcium Female Endothelium Vascular Themed Section: Research Papers |
| Zdroj: | British journal of pharmacology. 164(3) |
| ISSN: | 1476-5381 |
| Popis: | Controlling vascular tone involves K(+) efflux through endothelial cell small- and intermediate-conductance calcium-activated potassium channels (K(Ca)2.3 and K(Ca)3.1, respectively). We investigated the expression of these channels in astrocytes and the possibility that, by a similar mechanism, they might contribute to neurovascular coupling.Transgenic mice expressing enhanced green fluorescent protein (eGFP) in astrocytes were used to assess K(Ca)2.3 and K(Ca)3.1 expression by immunohistochemistry and RT-PCR. K(Ca) currents in eGFP-positive astrocytes were determined in situ using whole-cell patch clamp electrophysiology. The contribution of K(Ca)3.1 to neurovascular coupling was investigated in pharmacological experiments using electrical field stimulation (EFS) to evoke parenchymal arteriole dilatation in FVB/NJ mouse brain slices and whisker stimulation to evoke changes in cerebral blood flow in vivo, measured by laser Doppler flowmetry.K(Ca)3.1 immunoreactivity was restricted to astrocyte processes and endfeet and RT-PCR confirmed astrocytic K(Ca)2.3 and K(Ca)3.1 mRNA expression. With 200 nM [Ca(2+)](i) , the K(Ca)2.1-2.3/K(Ca)3.1 opener NS309 increased whole-cell currents. CyPPA, a K(Ca)2.2/K(Ca)2.3 opener, was without effect. With 1 µM [Ca(2+)](i) , the K(Ca)3.1 inhibitor TRAM-34 reduced currents whereas apamin (K(Ca)2.1-2.3 blocker) had no effect. CyPPA also inhibited currents evoked by NS309 in HEK293 cells expressing K(Ca)3.1. EFS-evoked Fluo-4 fluorescence confirmed astrocyte endfoot recruitment into neurovascular coupling. TRAM-34 inhibited EFS-evoked arteriolar dilatation by 50% whereas charybdotoxin, a blocker of K(Ca)3.1 and the large-conductance K(Ca) channel, K(Ca)1.1, inhibited dilatation by 82%. TRAM-34 reduced the cortical hyperaemic response to whisker stimulation by 40%.Astrocytes express functional K(Ca)3.1 channels, and these contribute to neurovascular coupling. |
| Databáze: | OpenAIRE |
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