Selected odors activate mDA-ORs expressed in heterologous cells as well as primary mDA neurons. a) Olfr287 was transiently transfected in HEK cells in combination with pCRE-SEAP. After transfection, cells were pulsed with the indicated odor molecules at 600 μM concentration. DMSO was used as negative control (cntrl). mDA-OR activation was measured with fluorimetric assay on culture medium. Odor response was calculated as fold-increase relative to control value. Data indicate mean ± st dev and are calculated on n = 4 independent experiments. b) Cells were transfected as in a) and pulsed with increasing concentrations of R-carvone, S-carvone, menthone and decanoic acid. Ringer’s solution or DMSO was used as control (cntrl). mDA-OR activation was calculated as in a). Data indicate mean ± st dev and are calculated on at least three independent experiments. *, p < 0.05; **, p < 0.01; *** p < 0.001. c) Ca2+ dynamics in primary DA neurons dissociated from the ventral midbrain of TH-GFP mouse. Normalized fluorescence ratio changes (340/380 nm) were measured in DA neurons loaded with Fura-2 AM and challenged with bath-applied odor mixture composed by 16 odorants at 200 μM each (recordings from N ≈ 30 neurons and repeated in n = 2 independent experiments). Images are presented in pseudocolour scale, as indicated. GFP fluorescence of DA neurons is shown. Scale bars indicate 10 μm. d) Experiment as in c). Primary neurons were stimulated with (R)- and (S)-carvone mixture at 600 μM each.