Ocular and nasal trigeminal detection of butyl acetate and toluene presented singly and in mixtures

To probe into the rules of trigeminal chemosensory agonism in a binary mixt ure of chemicals we measured, first, the detectability (i.e., psychometric) function for eye irritation and for nasal pungency of butyl acetate and to luene, singly. (To avoid olfactory biases, nasal pungency was measured in a group of anosmics, i.e., persons lacking a functional sense of smell.) The n, based on the detectability function obtained for the individual chemical s, we prepared mixtures where the 2 components varied in their relative pro portions but, if a simple rule of complete sensory agonism (in the sense of dose-additivity) were to hold, the mixtures should be as detectable as the reference concentration of each of the single chemicals. For both trigemin al endpoints (i.e., eye irritation and nasal pungency), the results showed that stimuli of relatively low detectability did show complete sensory agon ism, whereas stimuli of relatively high detectability fell short of complet e sensory agonism when compared with the detectability of the single substa nces. Further testing of additional binary and higher order mixtures will c onfirm whether or not a structure-activity model of trigeminal chemosensory impact of single chemicals, based on selected physicochemical parameters o f the stimuli, can also be applied to chemical mixtures.