期刊
BRITISH JOURNAL OF PHARMACOLOGY
卷 164, 期 3, 页码 922-933出版社
WILEY
DOI: 10.1111/j.1476-5381.2011.01447.x
关键词
astrocyte; brain slice; K(Ca)2.3; K(Ca)3.1; electrical field stimulation; laser Doppler flowmetry; neurovascular coupling; CyPPA; NS309
资金
- BBSRC CASE
- Boehringer Ingelheim Pharma GmbH Co KG
- Totman Medical Research Trust
- National Institutes of Health [P20-RR-16435, P01-HL-095488, R01-HL-044455, R01-HL-098243, T32 HL07944]
- British Pharmacological Society
BACKGROUND AND PURPOSE 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. EXPERIMENTAL APPROACH 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. KEY RESULTS 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 [Ca2+](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 mM [Ca2+](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%. CONCLUSION AND IMPLICATIONS Astrocytes express functional K(Ca)3.1 channels, and these contribute to neurovascular coupling.
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