Figure 2.

Active currents involved in generating and shaping dendritic spikes. A, TTX (0.5 μm) blocked the generation of local dendritic spikes and eliminated the supralinearity in the I-V plot, which actually became sublinear for high current intensities. B, 4-AP (5 mm) lowered the current threshold for the generation of dendritic spikes and increased their amplitude. 4-AP also increased the amplitude of dendritic spikes (from 67 ± 1 to 93 ± 3 mV; p < 0.0001; n = 8) and decreased their voltage threshold (from -45 ± 1 to -52 ± 1 mV; p < 0.0001; n = 8). For higher current intensities, back-propagating spikes (asterisk) could be recorded. C, Ba²⁺ (20 μm) increased the amplitude of dendritic spikes and decreased the current threshold for their generation, but the voltage threshold was not affected (from -48 ± 1 mV in control conditions to -48 ± 1 mV in the presence of Ba²⁺; p > 0.2; n = 8).