Figure 2.

Ion-dependent asymmetry in the IV relationship of fully activated HCN2 channels is maintained in excised inside-out patches. (A, C, and E) HCN2 currents obtained in response to activation at −145 mV for 1.5 s (left) and expanded views of tail currents upon depolarization to potentials between −100 and + 80 mV (right) when K was the only alkali metal presented to the channels (C) or Na and K were presented with quasi-physiological (A) and inverted (E) gradients. Each record is a single sweep filtered at 5 kHz and sampled at 20 kHz with no post hoc digital correction for uncompensated linear ionic or capacitive components. (B, D, and F) Plateau tail currents (determined by averaging current amplitudes between 7 and 9 ms after the test step) plotted versus the corresponding tail potential. Data are from records shown in A, C, and E, respectively. Data are representative of 4 (A and B), 6 (C and D), and 4 (E and F) similar recordings.