Fig. 8.

Blockers of K⁺ channels failed to unmask either the sADP or the PP in the absence of cholinergic stimulation. A, The sADP and PP were not observed after application of 1.2 μm TTX and K⁺ channel blockers (10 mmTEA, 5 mm 4-AP, 100 μmBa²⁺). Cholinergic stimulation, however, revealed a PP that was reversibly depressed by lowering Na⁺ from 152 to 26 mm in the external media (A1). Notice that robust Ca²⁺ spikes remained in low Na⁺, whereas the PP was reversibly depressed (A2). B, In addition, neither the sADP nor the PP was observed in pyramidal neurons loaded with 40 mm intracellular Cs⁺ and bathed in 1.2 μm TTX. As above, cholinergic stimulation revealed a PP that was reversibly depressed by lowering Na⁺ in the external media (B1). In this example, robust Ca²⁺ spikes also remained in low Na⁺, whereas the PP was reversibly depressed (B2).