Figure 6.
Kv4.1 contributes to slowly inactivating sustained outward currents in GCs. A, Average current traces for TEA-sensitive currents (ITEA) in LF-GCs (blue, n = 9) and HF-GCs (black, n = 4). B, Current density (pA/pF) of Ipeak and Isus at +30 mV for ITEA was not different in LF-GCs (blue) and HF-GCs (black). C, Average current traces for 4-AP-sensitive currents (I4-AP) in LF-GCs (blue, n = 9) and HF-GCs (black, n = 4). Da, I4-AP density in LF-GCs was significantly larger than that in HF-GCs (Ipeak, p = 0.001; Isus, p = 0.0001); Student's t-test. Db, The ratio of Iss to Ipeak (Iss/Ipeak) for IKv4.1 was significantly enhanced in LF-GCs (p = 0.0005). E, Whole-cell, voltage-gated K+ currents in LF-GCs at the beginning of the recording (blue) and after 15 min dialysis of Kv4.1 antibody (middle, red). The difference traces (right, red) represent currents mediated by Kv4.1 channel. Eb, Averaged I–V relationships of difference traces at its peak (Ipeak) and at the end of the pulse (Iss) from experiments shown in Ea. Fa, Records showing subsequent effects of 5 mm 4-AP after the maximal effect of Kv4.1 antibody in LF-GCs. The difference traces (right, gray) are defined as I4-AP-Kv4.1. Fb, Averaged I–V relationships of I4-AP-Kv4.1 from experiments such as Fa show no sustained outward currents. (Ga) Averaged IKv4.1 and I4-AP-Kv4.1 from LF-GCs are superimposed. Gb, Isus/Ipeak for IKv4.1 (red) and I4-AP-Kv4.1 (gray) of LF-GCs. H, Activation curve for IKv4.1 (red) and I4-AP-Kv4.1 (gray) in LF-GCs. Ia, Impact of the Kv4.1 antibody internal on K+ current during the bath application of 5 mm 4-AP and 40 μm 4-AP. Ib, Summary bar graphs showing inhibition of I/Imax by Kv4.1 antibody in the presence of 5 mm 4-AP (n = 4) or 40 μm 4-AP (n = 4) in the bathing solution. N.S. (not significant) p > 0.05, ***p < 0.001 by Student's t-test. Error bars indicate SEM. Values indicate mean ± SEM.