Age-dependent changes in I_f in perforated-patch recordings. (A) Normalized mean (±SEM) conductance-voltage relationships for I_f in SAMs isolated from young (black) or aged (red) mice in amphotericin B perforated-patch recordings. (insets) Schematic illustration of perforated-patch recording configuration and representative perforated-patch I_f current families in young (black) or aged (red) SAMs. Scale bars: 500 pA, 500 ms. (B) Mean (±SEM) V_1/2 values for I_f in young (black) and aged (red) SAMs in perforated-patch (PP, spotted bars) and whole-cell (WC, filled bars) recordings. P-values are comparisons between PP and WC for the same age (t tests); ‡, P < 0.05 compared with young in the same recording configuration (t tests).