Fig. 6. Late responses to subthreshold pulses. Responses obtained from another cell to current steps of (A) 200 ms and (B) 50 ms. Current steps are equally spaced by 33 pA. For depolarizing currents, the long-lasting steps provoke an outward rectification, indicated by the reduction of the spacing between voltage recordings after the hump (A,B) and also by the comparing the V/I relationship obtained at 54 ms (green line in A) and 195 ms (red line in A) corresponding to red and green symbols fitted by the dotted line in D. For hyperpolarizing steps, beyond 54 ms after the onset (green line in A) there is an inward rectification with a sag depolarization (arrows in A), suggesting an increase of membrane conductance. Consequently, at the peak of the hyperpolarization the limiting slope for hyperpolarizing currents is maximal (green symbols fitted by the continuous line in D). At the end of the current step, the return curves for depolarizations have a much faster decay than for hyperpolarizations. When the hyperpolarizing current steps are ended at 50 ms (B), the return curve last much longer than when steps are ended at 200 ms (A). This matches the drop in the limiting slope of the hyperpolarizing side of the V/I plot (compare the continuous line and red circles in D). After the long pulse, there is a rebound graded with the amount of hyperpolarization as shown in C (enlarged version of the yellow shaded area in A).