Figure 5. Effects of K⁺ channel blockers on I_NA.

All recordings were performed in external solution containing 20 mm K⁺ at a V_H of −80 mV. The neurones were pretreated for 1 min with each K⁺ channel blocker before the simultaneous application of 3 × 10⁻⁷ m NA. A, 4-aminopyridine (4-AP) inhibited I_NA in a concentration-dependent manner. B, the concentration-inhibition relationships for various K⁺ channel blockers on I_NA. All responses were normalized to the peak current induced by 3 × 10⁻⁷ m NA alone. Each point and the vertical bars represent the mean ±s.e.m. from 5 neurones.