Olfactory Deficits in 5XFAD Mice

5XFAD mice (3.5 or 7.5 months) were orally gavaged for 13 days with 100 mg/kg/day bexarotene. Odorants (heptanone, isoamyl acetate, limonene, and ethyl valerate; Sigma Aldrich, St. Louis, MO) were diluted 1 × 10⁻³ in mineral oil and applied to a cotton-applicator stick enclosed in a piece of plastic tubing32 (link). Odors were delivered for 4 successive trials (1 block), 20 seconds each, separated by 30 second inter-trial intervals, by inserting the odor stick into a port on the side of the animal’s home cage at day 13 of bexarotene treatment32 (link). Testing took place during the light phase of the animals’ (12:12) light:dark cycle. The duration of time spent investigating was defined as snout-oriented sniffing within 1 cm of the odor presentation port, and was recorded across all trials by a single observer blinded to genotype and treatment.