Disrupted AP firing patterns during 2 and 5 Hz stimulations in OMP KO ORNs. A, B, Recordings from ORNs expressing the mOR-EG receptor (A, WT; B, OMP KO), stimulated at increasing concentrations of eugenol. Stimuli at 2 Hz were followed by 5 Hz; odorant exposure was 100 ms. Recording bandwidth 0–5 kHz to display APs. C, D, The number of stimulations that led to the firing of APs was divided by the number of stimulations to yield the firing probability at 2 (C) and 5 Hz (D). OMP WT firing probability is represented with black lines and markers. OMP KO firing probability is represented with blue lines and markers. n = 6–7 ORNs; *p < 0.05; ***p < 0.005, unpaired Student's t test. All data are expressed as mean ± SEM.