Fig. 7. Use-dependent block of Na+currents by droperidol. (A ) Na+currents in control solution and in the presence of 10 μm droperidol activated by 10 consecutive depolarizing pulses at a frequency of 1 Hz (the number of the pulse is indicated near the corresponding trace). The currents were activated by 50-ms voltage pulses from −80 to −20 mV. (B ) Normalized amplitudes of Na+currents recorded in control solution and in the presence of 10 μm droperidol as a function of pulse number. Each current was normalized to the amplitude of the first Na+current recorded in control solution (seven somata ). (C ) Normalized amplitudes of the fast (circles) and slow (triangles) components of Na+current in control (open symbol) and in 10 μm droperidol-containing solution (filled symbols). Each current was normalized to the amplitude of the corresponding component of the first current recorded in control solution. Data from six somata .