Fig. 6. Comparison of current—voltage relationships of K⁺ currents of Kenyon cells (KC) and projection neurons (PN). Currents were recorded in external saline containing 100 nmoll^-1 tetrodotoxin (TTX) and were elicited by command voltage pulses between -80 mV and +120 mV (increment 10 mV; preceded by a prepulse to -120 mV for 1 s; holding potential -80 mV; see pulse protocol in Fig. 5). Current amplitudes were measured at the peak of the transient current component (arrows in Fig. 5A) and averaged (values are means ± S.E.M.; the numbers of observations are indicated). Projection neurons express higher current amplitudes than Kenyon cells and show a pronounced N-shaped I-V curve at positive membrane potentials. The I-V curve of outward currents of Kenyon cells is rather linear between -20 and +120 mV.