BK channels contribute to spike repolarization and fast afterhyperpolarzation (fAHP) in cultured CA1 pyramidal cells.

<p>(<b>a</b>) Whole-cell recording from CA1 pyramidal cell in WT organotypic slice culture. A 100 ms depolarizing current pulse was injected, evoking a train of action potentials (<b>a2</b>). Bath application of IbTX (100 nM) slowed repolarization of first action potential in the spike train and abolished the fAHP (<b>a1</b>). (<b>b</b>) Time course of IbTX effect on 1st action potential decay time (90%-10%) in a WT cell (same as in (a)). (<b>c</b>) Same test as in (a) applied to a BK^−/− slice culture (<b>c2</b>). 1st action potential was broader than in WT cells and lacked fAHP. IbTX had no detectable effect (<b>c1</b>). (<b>d</b>) Time course of IbTX effect on 1st action potential decay time (90%-10%) in a BK^−/− cell (same as in (c)). (<b>e</b>) Summary of 1st action potential decay time ± IbTX, in CA1 pyramidal cells from WT and BK^−/−. Decay time of WT cells under control condition was significantly shorter than for the other three groups (n = 4 in each group, <i>p</i><0.01). (<b>f</b>) Summary of fAHP amplitude (measured at the time point corresponding to the peak of the fAHP in WT cells). The fAHP amplitude was close to zero (not measurable) in BK^−/− and after application of IbTX in WT and BK^−/− cells.</p

Lack of BK channels aggravates cell death in CA1, CA3 and DG after <i>in vitro</i> ischemia (IVI).

<p>(<b>a,b</b>) Representative pseudocolour images showing PI fluorescence intensity as indicator of cell death measured 4 h, 8 h, 24 h, 48 h and 72 h after IVI. (<b>a</b>) BK^−/− and WT cultures without IVI (control cultures) maintained for 72 h. Regions of interests (CA1, CA3, dentate gyrus (DG)) are outlined. (<b>b</b>) BK^−/− and WT cultures at different time points after exposure to IVI. Scale bar  = 1 mm. (<b>c</b>) Time course of cell death measured as PI fluorescence in CA1 (<i>upper</i>), CA3 (<i>middle</i>) and DG (<i>lower</i>). Data are given as mean ± SEM; WT IVI: <i>n</i> = 44, BK^−/− IVI: <i>n</i> = 50, WT control: <i>n</i> = 25, BK^−/− control: <i>n</i> = 23; ***<i>P</i><0.005. Slice cultures were from a minimum of two pups per experimental set.</p

Targeted deletion of BK channel increases mortality and severity of brain infarction after transient middle cerebral artery occlusion.

<p>(<b>a</b>) Mortality within 7 h after reperfusion (in 8 WT vs. 8 BK^−/− mice tested), and the neurological deficit score (<b>b</b>) evaluated 7 h after reperfusion from seven WT and five BK^−/− mice. (<b>c</b>) Representative photomicrographs from coronal WT and BK^−/− brain sections (1 mm thick, from rostral (top) towards caudal (bottom)) stained with TTC 7 h after reperfusion. Lack of red staining indicates infarction. The infarction area of every brain section (<b>d</b>) and the resulting infarction volume of the ipsilateral hemisphere (<b>e</b>) are plotted. All data are given as mean ± SEM; WT: <i>n</i> = 7, BK^−/−: <i>n</i> = 5; *<i>P</i><0.05, **<i>P</i><0.01.</p

Cerebral blood flow and NMDA-induced excitotoxicity in WT and BK^−/− mice.

<p>(<b>a</b>) Cerebral blood flow (given as blood perfusion units [BPU], see also <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0015601#s2" target="_blank"><i>Methods</i></a>) was measured with laser Doppler flowmetry during anaesthesia (pre-ischemia), 10 min after onset of occlusion (intra-ischemia) and 10 min after reperfusion onset (post-ischemia), and is presented as mean ± SEM from 7 WT and 5 BK^−/− mice; **<i>P</i><0.01 (One-way ANOVA, followed by Tukey's post hoc analysis). (<b>b</b>) The neurological deficit score was evaluated 24 h after an intra-cerebral microinjection of 50 nmol of a NMDA solution in a volume of 500 nl. (<b>c</b>) <i>Left:</i> Representative WT and BK^−/− brain sections stained with TTC show the lesion area 24 h after NMDA-microinjection; bar: 4 mm. <i>Right:</i> The corresponding statistic based on the analysis of 3 WT and 3 BK^−/− mice. Data are given as mean ± SEM; *<i>P</i><0.05.</p