Kinetics of olfactory responses might largely depend on the odorant–receptor interaction and the odorant deactivation postulated for flux detectors
Experimental data together with modeling of pheromone perireceptor and receptor events in moths (Bombyx mori, Antheraea polyphemus) suggest that the kinetics of olfactory receptor potentials largely depend on the association of the odorant with the neuronal receptor molecules and the deactivation of the odorant accumulated around the receptor neuron. The first process could be responsible for the reaction times (mean about 400 ms) of the nerve impulses at threshold. The second process has been postulated for flux detectors such as olfactory sensilla of moths. The odorant deactivation could involve a modification of the pheromone-binding protein (PBP) that “locks” the pheromone inside the inner binding cavity of the protein. The model combines seemingly contradictory functions of the PBP such as pheromone transport, protection of the pheromone from enzymatic degradation, pheromone deactivation, and pheromone–receptor interaction. Model calculations reveal a density of at least 6,000 receptor molecules per µm2 of neuronal membrane. The volatile decanoyl-thio-1,1,1-trifluoropropanone specifically blocks pheromone receptor neurons, probably when bound to the PBP and by competitive binding to the receptor molecules. The shallow dose–response curve of the receptor potential and altered response properties observed with pheromone derivatives or after adaptation may indicate shortened opening of ion channels.