Supra- and subthreshold burst currents in preBötC intrinsic bursters. (A) Representative burst waveform (upper trace, CC recording) obtained under bath-applied CNQX (20 µM) and Cd²⁺ (200 µM). The net ionic current (lower trace) was calculated as the negative time derivative of membrane potential, –C × dV/dt, where C is the estimated membrane capacitance. (B) Normalized peak inward and outward net current, as measured throughout the burst (n = 19 neurons, each point averaged over five consecutive bursts; mean and SD). (C and D) TTX-sensitive Na⁺ current evoked by synthetic burst waveforms applied as the command voltage in VC. (C) Realistic burst waveform (upper trace) statistically matching natural bursts (see Fig. 1 E and Table 2) and evoked current from a representative neuron (middle trace, with dashed line range expanded in the lower trace). (D) Same as in C, with a uniform burst waveform, with identical action potentials and constant interspike interval. (E and F) The TTX-sensitive Na⁺ current evoked by the realistic (E) and uniform (F) waveforms, calculated across the 5 ms immediately preceding each action potential (n = 4; mean and SD). Note the exponential decay in F.