TRIGEMINAL AND OLFACTORY CHEMOSENSORY IMPACT OF SELECTED TERPENES

In Experiment 1, four normosmics and four anosmics (three congenital, one idiopathic) provided odor and nasal pungency thresholds, respectiv ely, for the following terpenes: Delta(3)-carene, p-cymene, linalool, 1,8-cineole, and geraniol, plus the structurally related compound cume ne. Additionally, all subjects provided nasal localization (i.e., righ t/left) and eye irritation thresholds. Trigeminally mediated threshold s (i.e., nasal pungency, nasal localization, and eye irritation) lay a bout three orders of magnitude above odor thresholds, which ranged bet ween 0.1 and 1.7 ppm. The results implied uniform chemesthetic sensiti vity across tasks and sites of impact. In Experiment 2, normosmics and anosmics provided odor and nasal pungency thresholds, respectively, f or three pairs of isomeric terpenes: alpha- and gamma-terpinene, alpha - and beta-pinene, and R(+)- and S(-)-limonene. Odor thresholds ranged between 1.4 and 19 ppm, that is, about an order of magnitude higher t han those of the previous terpenes, with no substantial differences be tween odor thresholds of members of a pair. Regarding chemesthetic imp act, only alpha-terpinene evoked nasal pungency. The overall outcome s uggests comparable trigeminal chemosensitivity between nose and eyes a nd between normosmics and anosmics, as shown before for homologous n-a lcohols. It also lends support to a previously derived solvation model of the chemesthetic potency of airborne substances, and indicates the likely importance of certain molecular-size restrictions for effectiv e trigeminal impact. (C) 1998 Elsevier Science Inc.