title: Perception of specific trigeminal chemosensory agonists.
abstract: The intranasal trigeminal system is a third chemical sense in addition to olfaction and gustation. As opposed to smell and taste, we still lack knowledge on the relationship between receptor binding and perception for the trigeminal system. We therefore investigated the sensitivity of the intranasal trigeminal system towards agonists of the trigeminal receptors TRPM8 and TRPA1 by assessing subjects' ability to identify which nostril has been stimulated in a monorhinal stimulation design. We summed the number of correct identifications resulting in a lateralization score. Stimuli were menthol (activating TRPM8 receptors), eucalyptol (TRPM8), mustard oil (TRPA1) and two mixtures thereof (menthol/eucalyptol and menthol/mustard oil). In addition, we examined the relationship between intensity and lateralization scores and investigated whether intensity evaluation and lateralization scores of the mixtures show additive effects. All stimuli were correctly lateralized significantly above chance. Across subjects the lateralization scores for single compounds activating the same receptor showed a stronger correlation than stimuli activating different receptors. Although single compounds were isointense, the mixture of menthol and eucalyptol (activating only TRPM8) was perceived as weaker and was lateralized less accurately than the mixture of menthol and mustard oil (activating both TRPM8 and TRPA1) suggesting suppression effects in the former mixture. In conclusion, sensitivity of different subpopulations of trigeminal sensory neurons seems to be related, but only to a certain degree. The large coherence in sensitivity between various intranasal trigeminal stimuli suggests that measuring sensitivity to one single trigeminal chemical stimulus may be sufficient to generally assess the trigeminal system's chemosensitivity. Further, for stimuli activating the same receptor a mixture suppression effect appears to occur similar to that observed in the other chemosensory systems.
authors.affiliation: Monell Chemical Senses Center, Philadelphia, PA, USA. frasnelli@yahoo.com
authors.forename: J
authors.initials: J
authors.lastname: Frasnelli
authors.forename: J
authors.initials: J
authors.lastname: Albrecht
authors.forename: B
authors.initials: B
authors.lastname: Bryant
authors.forename: J N
authors.initials: JN
authors.lastname: Lundström
mesh_terms: D000328:Adult; D015220:Calcium Channels; D003511:Cyclohexanols / Q000494:pharmacology; D000077591:Eucalyptol; D005260:Female; D006801:Humans; D008297:Male; D008610:Menthol / Q000494:pharmacology; D039821:Monoterpenes / Q000494:pharmacology; D009149:Mustard Plant; D009419:Nerve Tissue Proteins / Q000819:agonists*; D009666:Nose / Q000294:innervation; D010938:Plant Oils / Q000494:pharmacology; D011984:Sensory Receptor Cells / Q000502:physiology; D000074025:TRPA1 Cation Channel; D050053:TRPM Cation Channels / Q000819:agonists*; D050051:Transient Receptor Potential Channels / Q000819:agonists*; D014276:Trigeminal Nerve / Q000166:cytology / Q000502:physiology*; D055815:Young Adult
chemical_list: D015220:Calcium Channels; D003511:Cyclohexanols; D039821:Monoterpenes; D009419:Nerve Tissue Proteins; D010938:Plant Oils; D000074025:TRPA1 Cation Channel; C473350:TRPA1 protein, human; D050053:TRPM Cation Channels; C425966:TRPM8 protein, human; D050051:Transient Receptor Potential Channels; D008610:Menthol; D000077591:Eucalyptol; C027793:mustard oil