Dose-response relationships in an olfactory flux detector model revisited

A simple model of an odorant flux detector including odorant uptake, activation of odorant receptor molecules and enzymatic odorant deactivation can produce different types of static dose-response relationships. Depending on the binding characteristics of the odorant to the receptor molecule and to the deactivating enzyme, the receptor occupation by the odorant as related to the odorant uptake is quasi-hyperbolic, linear or, close to saturation, steeper than linear. In Rospars et al. (2003, Chem. Senses, 28: 509-522) a note contributed by both of us stated erroneously that an equation describing these relationships given previously (Kaissling, 1998, Chem. Senses, 23; 99-111; Kaissling, 2001, Chem. Senses, 26: 125-150) was incorrect. We show here that the difference in equations was due to a simplifying assumption in Rospars et al. (2003) about the deactivating enzyme, we summarize briefly the properties of the correct equation of Kaissling (1998, 2001) and we discuss the relation with the model studied in Rospars et al. (2003).