Molecular Boundaries For Trigeminal Chemosensory Impact

University Of California, San Diego, La Jolla CA

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Abstract

DESCRIPTION (provided by applicant): The proposal aims to define the molecular boundaries of size, shape, structure, and relevant physicochemical properties for a volatile organic compound (VOC) to act as an effective trigeminal (i.e., chemesthetic) stimulus in humans. Chemesthetic responses in the mucosae of the face to airborne chemicals include nasal pungency (i.e., irritation) and eye irritation, two frequently mentioned adverse symptoms arising from indoor (e.g., sick building syndrome) and occupational environments. This proposal is a follow-up of our previous work exploring the physicochemical basis for the production of these chemesthetic responses by VOCs. Systematic chemosensory testing of members of homologous chemical series has revealed that a homolog can be reached where the ability to evoke these trigeminal responses begins to fade, and finally disappears for all ensuing homologs, constituting a "cut off" effect. The proposal focuses on the two or three homologs from each series at the boundary of the cut off effect, and will measure the sensory responses of nasal pungency, nasal localization, and eye irritation. From each substance selected to be tested, we will obtain stimulus-response (psychometric) functions spanning the range from chance detection to virtually perfect detection in order to identify the precise homolog reaching the cut off point in each homologous series. By means of chemical modeling and by additional sensory testing of rigid chemical structures molded on the molecular parameters of the cut off homologs, we will define the molecular and physicochemical boundaries for any volatile compound to be able to act as an effective trigeminal chemosensory stimulus. Knowledge of such boundaries has important implications for both basic and applied aspects of trigeminal chemoreception. From a basic perspective it will contribute to the chemical characterization of the trigeminal reception process(es), from an applied perspective it will allow to understand and prevent adverse sensory reactions from air pollutants.