Dendrotoxin has little effect on spike width and increases repetitive firing. A, B, Current-clamp recordings from a dissociated cell (A) and a cell recorded in situ in control (A₁,B₁) and 1 μm DTX-I (A₂, B₂). After perfusing with 1 μm DTX-I the cells increased their firing, and the first spike was the same width as in control. C, A series of pulses of increasing magnitude were delivered to the cell inB to show changes in threshold and repetitive firing properties in DTX. DTX-I (filled circles) increased the number of spikes fired at each level of current.D, For three cells with similar thresholds the initial firing frequency (1/first interspike interval) is plotted against the current normalized to the control threshold current. At every current level the frequency in DTX (filled circles) was higher than in control (open circles).