Figure 1. Block of Kv1 channels results in the generation of random bursts of increased somatic activity without altering the baseline firing rate.

The firing rate of Purkinje neurones were monitored in cerebellar slices using a differential amplifier. A, average firing rate of a tonically firing Purkinje cell (calculated every 500 ms) before and after bath application of 142 nm α-DTX. Brief transient increases in the average firing rate are apparent in the presence of α-DTX although the baseline firing rate remains the same. B, interspike interval histogram of the cell described in A in control solution and in the presence of α-DTX. The average firing rate did not significantly alter following α-DTX application. C, instantaneous firing rate (1/interspike interval) of the Purkinje cell shown in A in the presence of α-DTX. Note the large transient increases in the firing rate. D, sample raw data of the spontaneous firing of the same Purkinje cell as in A in the presence of α-DTX. The transient increases in the firing rate correspond to the bursts of increased activity. E, effects of bath perfusion of 142 nm α-DTX on the pattern and rate of activity of a Purkinje cell with the trimodal pattern of activity. α-DTX significantly reduced the pattern duration (**P < 0.01, one-way ANOVA). F, in addition to reducing the pattern duration, α-DTX also resulted in the spontaneous bursts of increased somatic activity during the tonic phase of the trimodal pattern. Instantaneous firing rate and raw data from the tonic phase of the cell shown in E in the presence of α-DTX.