Ligand tuning of larval olfactory neurons in wild-type animals. (a) Odor-response profiles of the three OSNs most sensitive to ethyl butyrate, measured at axon termini of a given OSN in the antennal lobe, against a panel of 22 odorants (10-2 odor dilution) and paraffin oil (solvent). Responses are shown as described in Figure 1d. Chemical structures and categorization by functional group of 22 odorants are at top left. Traces from n = 7–9 animals per stimulus are stacked. (b) Responses of Or35a, Or42a, and Or42b OSNs to an ethyl butyrate concentration series and paraffin oil (solvent) represented as ΔF/F (%) (scale at right). Traces from n = 6–8 animals per genotype and stimulus are stacked.