Figure 1. Lack of activation of K_ACh channels by inositol-containing phospholipids and PE in inside-out patches.

A-D, cell-attached patches were formed with 10 μM ACh in the pipette. Channels were activated when ACh was present in the pipette. Upon formation of inside-out patches, channels closed immediately. PIP₂ (50 μM), PIP (50 μM), PI (50 μM) or PE (100 μM) was then applied to the cytoplasmic side of the membrane for ≈10 min. GTPγS (10 μM) was then applied for ≈1 min, and then purified bovine βγ subunit (50 nM) applied subsequently. Although not shown in C, the βγ subunit activated the channels when applied ≈5 min after the GTPγS application. In D, occasional openings of one K_ATP channel can be seen. In E, no ACh was added to the pipette solution. Membrane potential was held at -60 mV. All tracings were filtered at 100 Hz.