Quantitative analysis on odor intensity and quality of optical isomers in turtle olfactory system.

No systematic electrophysiological study on differences in odor intensity and quality between optical isomers has been carried out. In the present study, we measured the turtle olfactory bulbar responses to six pairs of highly pure optical isomers and compared the differences in odor intensity and quality between the optical isomers. The results obtained indicated that with all odorants tested, there was no difference in odor threshold and intensity in the whole concentration range examined between optical isomers. The difference in odor quality of optical isomers was evaluated by a quantitative cross-adaptation method in which odorant concentration was varied. The degree of cross adaptation between optical isomers greatly varied with species of odorants. The rank order of the magnitude of the differences in odor quality between optical isomers was carvone greater than beta-citronellol greater than menthol greater than hydroxycitronellal greater than citronellal greater than limonene.