Figure 2

I _h voltage dependence and its modulation by cAMP. (A) Top: Family of tail currents from neocortical neurons at P0 (left) and at P30 (right). For both examples, different durations of the tail currents are displayed on return to −65 mV from preceding 2-second voltage steps between −130 and −60 mV (see voltage protocol). Tail current amplitudes were measured after the cessation of capacitive transients (dotted vertical line). The time scale is representative for both ages. Bottom: Population data of steady-state activation curves without intracellular cAMP, depicted as mean relative tail currents, plotted against the preceding test potential. For illustration purposes the means were fitted using a Boltzmann function, although during analyses each single neuron was fitted. For individual experimental values compare (B). (B) Population data on the modulation of the half-maximal activation voltage (V_1/2) by cAMP at P0, P1 and P30. The V_1/2 did not differ between ages when cAMP was absent from the intracellular solution (open bars). Adding 100 μM cAMP intracellularly shifted the V_1/2 at P0 and P1 to more depolarized voltages, but did not change the V_1/2 at P30 (lower part, grey bars). (C) Age dependence of the current deactivation at −120 mV for a P0 and a P30 neuron in a scaled example. The current was fitted by a single exponential equation (red) and showed a prolonged deactivation at P0. *Indicates significance P < 0.05 (ANOVA with Tukey post-hoc test).