Methyl valerate

Different odorants (methyl valerate, isoamyl acetate, ethyl tiglate, and 2-heptanone; Sigma-Aldrich, USA) were used at concentrations between 0.12% and 11% of saturated vapor. A cleaned air stream was used for odorant dilution from saturated vapor. A flow dilution olfactometer ^{31 (link)} was designed to provide a constant airflow over the nares. A vacuum-controlled odorant delivery, where the vacuum was switched off during the odorant presentation. Separate Teflon tubing lines were used for each odor to avoid cross-contamination. In a subset of experiments, the time course and relative concentration of odors were confirmed with a photo-ionization detector (PID; Aurora Scientific, Aurora, ON). During imaging trials odorants were either delivered for 2–3 s with a 60-s delay between presentations, or odors were repeatedly presented with a 6-s interstimulus interval (adaptation trials).

A variety of monomolecular odorants was selected based on their solubility and previous use in olfactory research involving rats. All odorants (amyl acetate (AA), methyl valerate (MV), ethyl butyrate (EB)) and tastants (HCl, sucrose) were reagent grade and purchased from Sigma (Sigma-Aldrich, St. Louis, MO). Odorants were stored in the dark under nitrogen. Only AA was tested behaviorally, all three odors were tested using optical calcium imaging.