Figure 6.
Most NTS CA neurons express substantial, early transient outward current (IKA). A, In a representative NTS CA neuron expressing a large IKA, depolarizing steps evoked currents with a large, early component that rapidly decayed to steadier levels within 200 ms. Under voltage clamp, neurons were preconditioned at −100 mV before stepping to test levels starting at −100 mV and increasing by +10 mV with each sweep. B, 4AP blocked the early, transient current, consistent with IKA. Currents were evoked by a test step to 0 mV after a conditioning step to −100 mV without (control) and with 5 mm 4AP. C, Plots of mean activation and inactivation curves for IKA (peak current minus persistent current) indicate a critical voltage dependence near resting potentials for these neurons (n = 61). Error bars indicate SEM. D, Histogram showing the distributions of the IKA and IKV current amplitudes for second order neurons at −30 mV.