Fig. 1.

Enhanced dendritic excitability in Kv3.3 KO Purkinje cells (PCs). A and B: in the presence of Na⁺ channel blocker TTX (100 nM) square pulse somatic current injections were applied to evoke dendritic Ca²⁺ spikes. Recordings display Ca²⁺ spiking at threshold for a wild-type (A) and Kv3.3 KO (B) PCs. In these examples, current threshold was 1.35 nA in the wild-type recording and 0.65 nA in the Kv3.3 KO recording. C and D: Ca²⁺ spikes elicited by long duration (4 s) current ramps. Current threshold was determined as the current amplitude at the time of spiking onset and was 1.47 nA for wild-type (C) and 0.99 nA for Kv3.3 KO (D) recordings in these examples. Protocols are demonstrated in gray beneath voltage traces in B and D. E: population data comparing Ca²⁺ spike current threshold from wild-type (n = 7) and Kv3.3 KO (n = 7) PCs for square pulse and slow ramp protocols. Asterisks denotes statistical significance (P < 0.01); error bars are SD. I thresh, current threshold; I inj, current injection.