β4-containing BK channels do not contribute to whole-cell BK channel currents.

<p>(A) In situ hybridization showing regions of β4 expression in a mouse brain. Arrow points to high levels of expression in the CA3. (B) Hippocampal area CA3 shows robust β4 expression. Scale bar = 200 µm. (C) Bright field image showing a whole cell electrode in the CA3. Scale bar = 500 µm. (D) Fluorescent image of a CA3 pyramidal cell filled with Alexa fluor 568 after whole cell patch clamp recording. Scale bar = 50 µm. (E) Overlaid traces from a representative cell showing total potassium current and the residual potassium current after application of a BK channel blocker. (F) Schematic overlap between paxilline- and iberiotoxin-sensitive currents when β4-containing BK channels contribute to whole-cell current. (G) Schematic overlap between paxilline- and iberiotoxin-sensitive currents when β4 containing BK channels do not contribute to whole-cell current. (H) Example paxilline-sensitive BK channel current from a representative cell. (I) Example iberiotoxin-sensitive BK channel current from a representative cell. (J) Quantitation of mean paxilline (pax)- and iberiotoxin (ibtx)-sensitive currents from CA3 pyramidal cells.