Figure 2.

Electrophysiological maturation of NPCs in high cAMP (IBMX), with voltage-dependent ionic currents and action potentials. In (A), voltage clamp recordings on NSCs differentiated for 7 days in IBMX. Holding potential −80 mV, 100 ms pulse duration from −70 to 70 mV at 10 mV increments, with an average of 5 consecutive sweeps. Leak and capacitive currents were subtracted using a P/-4 protocol (see text). In (A′), the same Na⁺-currents from (A) are shown in an expanded time frame. In (B), voltage-dependent activation of K⁺- and Na⁺-conductance for representative cells cultivated in basal medium, BDNF and IBMX for 7 days, fitted with a Boltzmann equation of the form f(V) = 1/(1 + exp[(V_1/2 − V)/V_slope]). In (C), trends of action potentials induced in current clamp of a cell cultivated in IBMX, and for comparison, one simple potential evoked in a cell cultivated with BDNF; pulse duration 1 s, −20 to 70 pA at 10 pA increments, both figures represent a simple trace at +40 pA. In (D), frequency-current (fI) relationship for the sample cell and for two other representative cells cultivated in basal medium and in BDNF alone. In (E) and (F), Na⁺- and K⁺-current densities, respectively, were calculated across three different culture conditions, basal medium, BDNF and IBMX; for this, cell capacitance was calculated from a mono-exponential curve fitting in voltage-clamp mode, using a −10 mV hyperpolarizing pulse, repeated in 50 sweeps and averaged. Na⁺- and K⁺- peak currents were determined from 5 and 100 data points, respectively, from the I–V traces (5 sweeps).