Figure 9. Spontaneous bistability can be enhanced by blockade of calcium-activated potassium channels.
A, internal BAPTA rapidly increased the spontaneous firing frequency of Purkinje neurons. A continuous histogram of action potential firing rate demonstrates the increase in frequency following establishment of a whole-cell recording using an intra-pipette solution containing 20 mm BAPA (see Methods). Voltage traces (right) show action potentials in the cell-attached and whole-cell mode (a; firing rate 55 Hz) and 15 s following break-in (b, firing rate 140 Hz). B, in another Purkinje neuron, continued dialysis with BAPTA led to a spontaneous bistable activity pattern (left). The inset (a) shows state transitions at a faster time base. Addition of ZD 7288 (40 μm) enhanced the spontaneous bistable activity pattern (right); stereotyped bursts of firing were interspersed with periods of quiescence lasting several minutes. The inset (b) shows state transitions on a faster time base.