Fig. 8.

A-type current-mediated changes in apical tuft excitability: model. A₁: a reconstructed PFC L5 pyramidal cell. Inset: on each model run, only one apical tuft branch will be altered (e.g., red). A₂: dendritic intracellular Ca²⁺ concentration ([Ca²⁺]; red) and dendritic voltage (V_m; red) recorded from a location marked by red circle in A₁. Somatic AP is black. A change in dendritic g_KA from 400 (left) to 385 pS/μm² (right) was made in one apical tuft branch. Dendritic voltage waveform is copied from that at left, colored gray, and superimposed at right. Arrow indicates broadening of voltage waveform at the base. Inset: blowup of voltage waveforms (scales, 10 mV and 5 ms). A₃: peak amplitude of Ca²⁺ signal from each tuft dendrite plotted against g_KA in that dendrite. Each color (yellow, green, and blue) represents uniform (global) g_KA in the apical trunk and tuft (650, 700, and 750 pS/μm², respectively). Red circles indicate data from the red branch in A₁. Dashed horizontal line represents a baseline level of AP-Ca²⁺ signal associated with high levels of local g_KA. B₁ and B₂: same as in A₁ and A₂, except global apical g_Na, g_KA, and g_Ca were reduced to mimic moderate amplitude changes. Local g_KA was gradually changed from 800 to 300 pS/μm² in the red dendrite only (local g_KA values indicated above Ca²⁺ signals). B₃: same organization of curves as in A₃. Note that in this model, a relative increase in Ca²⁺ signal above baseline level (dashed horizontal line) is less pronounced than in A₃, hence “moderate.”