Figure 4. Time course of I_mtx and the increments in intracellular Ca²⁺ and Na⁺ concentrations.

Concomitant measurements of current using patch clamp and intracellular Na⁺ and Ca²⁺ with fluorescent indicators. A, a typical experiment showing the time course of I_mtx activation. The current was evoked with continuous ramps from −100 to +100 mV. The ramps were interrupted to perform voltage steps from −140 to +120 mV in increments of 20 mV (V_h = 0 mV) to obtain I-V curves. Voltage protocols shown in the inset. Vertical arrows indicate the time of addition of 500 pm MTX. B, time course of the changes in [Ca²⁺]_i in response to MTX monitored with the fluorescent indicator fura-2. C, time course of the changes in [Na⁺]_i monitored with the fluorescent indicator SBFI. Time scale is the same in all panels (shown at the bottom of the figure). Representative traces are shown from eight experiments.