Olfactory sensitivity for “green odors” (aliphatic C 6 alcohols and C 6 aldehydes) — A comparative study in male CD-1 mice ( Mus musculus ) and female spider monkeys ( Ateles geoffroyi )

Using a conditioning paradigm, the olfactory sensitivity of six male CD-1 mice for “green odors”, a group of eight structurally related aliphatic C 6 alcohols and aldehydes known to exert anxiolytic and stress-reducing effects, was investigated. With all eight stimuli, the animals discriminated concentrations ≤ 0.03 ppm (parts per million) from the solvent, and with three of the eight stimuli the best-scoring animals were even able to detect concentrations ≤ 0.03 ppb (parts per billion). Three female spider monkeys tested in parallel were found to detect the same eight stimuli at concentrations < 1 ppm, and with six of the eight stimuli the best-scoring animals detected concentrations ≤ 0.1 ppm. Analysis of odor structure–activity relationships showed that in both species the type of functional group attached to the aliphatic C 6 backbone of the odorant molecules systematically affected their olfactory sensitivity whereas the presence/absence of a double bond did not. In the mice, but not in the spider monkeys, the position of a double bond and the cis/trans-configuration of the odorant molecules also had a systematic effect on detectability of the “green odors”. A comparison of the detection thresholds between the two species tested here and those obtained in human subjects suggests that the number of functional olfactory receptor genes is a poor predictor of a species' olfactory sensitivity for “green odors”.