Odorant-receptor-dependent responses to PDE inhibitor IBMX. A, Responses to a 1 s stimulation of 1 mm of the PDE inhibitor IBMX from M71-GFP OMP WT and OMP KO (black and blue trace) ORNs. None of the parameters measured was significantly different (C, left column). n = 10–14. B, 1 s IBMX stimulation of mOR-EG-GFP OMP WT and OMP KO ORNs. mOR-EG GFP OMP KO peak responses were significantly larger than those of mOR-EG-GFP OMP KO ORNs. The current at the end of the 1 s (Current @ 1 s) stimulation is indicative of a larger residual current at the end of the stimulation as a result of an altered termination phase of OMP KOs (C, right column). mOR-EG-GFP OMP KO ORNs also fire twice as many APs than OMP WTs. n = 5–14 ORNs. *p < 0.05; ***p < 0.005, unpaired Student's t test. All data are expressed as mean ± SEM.