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. 2006 Nov 29;26(48):12576–12586. doi: 10.1523/JNEUROSCI.3080-06.2006

Figure 4.

Figure 4.

Effect of ω-agatoxin-IVB on spontaneous firing properties of cerebellar PCs from +/+ mice. A, Example of the effect of ω-agatoxin-IVB on the time course of instantaneous spontaneous firing frequency of a +/+ PC, recorded in cell-attached mode at 34°C and with synaptic blockers in the control solution. The cell fires tonically in control. In the presence of BSA (25 μg/ml), the firing rate increases slightly for ∼5 min. When ω-agatoxin-IVB (100 nm) is added to the superfusate, a dramatic increase in the frequency is initially observed, which develops into an irregular bursting firing pattern. The cell then enters a quiescent state for the rest of the recording in cell-attached mode (∼5 min). Two-second blocks of data are shown above the graph for the periods indicated by the arrows. Similar data were obtained in three other cells that were initially firing tonically. B, Expansion of part of Figure 4A to show the initial transient increase in firing frequency after ω-agatoxin-IVB application, plotted as fold increase (solid line). The simultaneous fold increase in the CV of the firing frequency is superimposed (filled circles). Similar data were obtained in three other cells that were initially firing tonically. C, Average spontaneous firing frequency in control, BSA, and ω-agatoxin-IVB for +/+ PCs (n = 6). The slight increase in frequency in BSA is not statistically significant (p = 0.1, paired t test). D, Firing evoked by a 600 pA (top traces) or a 900 pA (bottom traces) current pulse of 400 ms duration in control (left) and after >5 min in the presence of ω-agatoxin-IVB (right) in a +/+ PC. Under control conditions, the cell is able to fire action potentials throughout the duration of the 600 and 900 pA steps, whereas after ω-agatoxin-IVB, the 600 pA current is no longer sufficient to evoke firing (top right). In ω-agatoxin-IVB, the cell is still able to fire in response to a 900 pA current injection, although only with a few initial spikes accommodating to a plateau (bottom right), as typically seen in du2J/du2J PCs.