CONCENTRATION AND MEMBRANE FLUIDITY DEPENDENCE OF ODOR DISCRIMINATIONIN THE TURTLE OLFACTORY SYSTEM

In the present study, we examined the concentration dependence of odor discrimination in turtle olfactory bulbar responses using the cross-a daptation technique. In the odorant pairs with diverse molecular struc tures, the degree of discrimination was unchanged or only slightly dec reased with an increase in odorant concentrations, suggesting that odo rants are well discriminated even at high concentrations. In the odora nt pairs with closely related molecular structures, the degree of disc rimination was decreased with an increase in odorant concentrations. A n increase in the temperature of turtle olfactory epithelium also decr eased the ability to discriminate these odorants. There was a good cor relation between changes in the odor discriminating ability induced by an increase in odor concentrations and those induced by a temperature increase. The liposomes were made of lipids extracted from the turtle olfactory epithelia and changes of their membrane fluidity induced by adsorption of odorants were monitored with DPH. There was a good corr elation between a decrease in odor discriminating ability and the memb rane fluidity changes induced by odorants. We suggest that decreases i n odor discriminating ability induced either by an increase in odor co ncentration or by a temperature increase are ultimately caused by chan ges in the membrane fluidity.