Fig. 8.
Sensitivity to 10–50 μM 4-aminopyridine (4-AP) varies with zone. A: currents in a PZ calyx in response to a +21-mV voltage step. Current was reduced by 29% in the presence of 10 μM 4-AP. The subtracted current (Isubtracted) activated rapidly and showed moderate inactivation. B: I-V plots show control currents, currents in the presence of 10 μM 4-AP, and the 4-AP-sensitive current (Isubtracted). Current amplitude was measured at the end of each 40-ms voltage pulse. C: 10–50 μM 4-AP reduced outward current by 35 ± 4.2% in PZ calyces (n = 7), which was significantly greater than the reduction of 21 ± 3.8% in CZ calyces (n = 6). *P < 0.05, t-test.