Fig. S5.

Cl current at response threshold. Similar experiment as in Fig. 7 but in another ORN with even less receptor current. Near-threshold odorant response (∼1.2 pA; black trace) elicited by a weak odorant stimulus [30-ms, 100 μM (+)-limonene pulse] is subjected to successive 150-ms, 300 µM NFA pulses with increasing time delays (at 150-ms increments; color coded), showing an obvious suppression, confirming the existence of Cl current in threshold response. Each trace is the average of >15 stimulus trials; duration between successive stimulus trials is 60 s. The 50 μM verapamil, 1 μM mibefradil, and 500 nM TTX were included in the pipette and all bath solutions to eliminate the action potentials. Signals are low-pass filtered at 20 Hz (eight-pole Bessel) to minimize the noise.