Stabilization and reactivation of N-type Ca²⁺ channels by PIP₂ in inside-out membrane patches. A, Representative current trace (I_tail(+100)) for the experiments shown in this figure, evoked by the indicated voltage protocol. Dashed line indicates zero-current level. B, Plotted are the normalized amplitudes of I_tail(+100) in control bath solution or with a 2 min application of PIP₂ (10 μm) added to the bath solution immediately after excision (bar). Inset shows summarized normalized amplitudes of I_tail(+100) 5 min after patch excision with or without a 2 min PIP₂ application immediately after excision. ^**p < 0.01. C, Representative time course of rundown and reactivation of I_tail(+100) by PIP₂ application during the period shown by the bar. The normalized amplitudes of I_tail(+100) during the experiment are plotted. D, Summary of reactivation of I_tail(+100) by PIP₂, applied 2 min after patch excision for 2 min. Minimum current after patch excision and maximum current after PIP₂ application are plotted for 10 patches. In all panels, I_tail(+100) is normalized by that obtained immediately after patch excision (0 time).