Fig. 6.
A: family of outward currents evoked by the protocol described previously but using K+ pipettes. The outward current activated rapidly and then relaxed slowly throughout the remainder of the 500-ms test pulse. B: the currents were greatly attenuated in the presence of 1 mM 4-aminopyridine (4-AP). C: summary of the current-voltage plot for eight experiments in control conditions (■) and in the presence of 4-AP (▲). The current activated at −50 mV and showed outward rectification upon stepping to more positive potentials. 4-AP reduced the maximum current by 73% (n = 8, P < 0.0001). D: current activation and inactivation properties. The current activated (■) at potentials positive to −80 mV and was maximally active at +40 mV. V1/2 of activation was −21 ± 0.7 mV (n = 38). An inactivation protocol (conditioning pulses of 2-s duration in the range −100 to +20 mV stepping to a test potential of +40 mV) yielded the inactivation curve (▲). Inactivation began at potentials positive to −70 mV and reached a plateau at about 0 mV although 30% of the current was still available.