Figure 1.

Basal action potential activity in olfactory receptor neurons. A–C show responses from isolated ORNs expressing the identified odorant receptors mOR-EG, M71, and I7 stimulated with their respective ligands eugenol, acetophenone, and heptanal. (D–F) Recordings in the absence of stimulation to monitor basal spike firing activity, same three cells as above. Red, low-pass (50 Hz) filtered recordings to display the underlying fluctuations of the receptor current. The Ca²⁺-activated Cl⁻ channel blocker niflumic acid (300 µM, applied from 30 to 60 s) entirely abolished basal activity. (G–I) Expanded view of the same traces as in D–E to show current fluctuations.