Figure 2.

AP bursting in SP cells requires a Ni²⁺-sensitive conductance that generates an ADP. A, Bath perfusion of 100 μm Ni²⁺ abolishes burst firing in an SP cell (left; 480 pA current step) but has no effect on the regular firing of an SL cell (right; 240 pA step). B, Summary of the effect of 100 μm Ni²⁺ on the averaged instantaneous AP frequency in SP (left; n = 5) and SL cells (right; n = 4). C, APs recorded just above rheobase in an SP cell (left) and an SL cell (right) before (black trace) and after (gray trace) bath perfusion of 100 μm Ni²⁺ (same cells as in A). In each panel, APs in the dashed boxes (main panel) are shown expanded and aligned in the inset. Ni²⁺ blocks an ADP in the SP cell but has no effect on the afterhyperpolarization in the SL cell.