Fig. 6

Sim1-Puro selected cultures exhibit action potential firing and voltage gated currents consistent with neuronal maturation. a Sub- and supra-threshold voltage responses recorded under current clamp in a 1p +2 cell with 50 msec square pulse injection (6 and 8 pA). b Examples of cells firing single (1p +11), adapting (1p +11), and multiple (1p +10) action potentials during an 800 msec depolarizing pulse (44 pA). c Currents mediated by tetrodotoxin-sensitive sodium channels evoked by steps from −100 to +60 mV from a holding potential of −80 mV (below). Peak inward current plotted as a function of step potential (1p +13; Cs-glucuronate internal solution). d Outward currents mediated by voltage-gated potassium channels for steps from −100 to +60 mV from a holding potential of −80 mV recorded in 0.5 μM tetrodotoxin (TTX) alone and in TTX plus 5 mM 4-aminopyrridine (4AP) (below). 4AP-sensitive currents revealed by subtracting current in TTX and 4AP from current in TTX alone (1p +8, K-glucuronate internal solution). e Current–voltage relation for steady-state current recorded in TTX plus 4AP (open symbols) and for peak 4AP-sensitive current (filled symbols)