2009 Abstracts - Association for Chemoreception Sciences

#P318 Poster session VII: Chemosensory Psychophysics IIOral irritation elicited by menthol and cinnamaldehyde (CA):self- and cross-desensitizationE. Carstens, Mirela Iodi Carstens, Karen ZanottoUniversity of California, Davis Davis, CA, USAMenthol and CA are used in oral hygiene products for theirrefreshing sensory properties, but are irritating at higherconcentrations. We investigated if they exhibit self- and crossdesensitizationof their oral irritancy. Using a 2-alternativeforced-choice (2-AFC) paradigm, either menthol (19.2 , 28.8 mM)or CA (15.2, 30.4 mM) was briefly applied by filter paper to oneside of the dorsal tongue, with vehicle similarly applied to theother side. Following variable intervals, either menthol or CAwas applied bilaterally and subjects stated on which side theyexperienced greater irritation, followed by ratings of irritantintensity on each side using a labeled magnitudescale. Desensitization was manifest by a significant proportion ofsubjects choosing the vehicle-treated side as having strongerirritation, and assigning significantly higher ratings to that side.Menthol 19.2 mM exhibited significant self-desensitization andcross-desensitized irritation elicited by 15.2 mM CA applied 5but not 30 min later. CA 30.4 mM (but not 15.2 mM) crossdesensitizedirritation evoked by 28.8 mM menthol applied 5 and30 min later, and exhibited self-desensitization. These data areconsistent with self- and mutual cross-desensitization of mentholand CA-evoked responses of neurons in superficial layers oftrigeminal subnucleus caudalis. Using calcium imaging of culturedrat trigeminal ganglion neurons, we observed CA suppression ofmenthol-evoked responses, suggesting a peripheral site ofinteraction of these compounds on trigeminal nerve endings.#P319 Poster session VII: Chemosensory Psychophysics IIEvidence that repeated threshold testing can alter the perceivedintensity of tasteBarry Green 1,2 , Juyun Lim 31The John B. Pierce Laboratory New Haven, CT, USA,2Dept. of Surgery (Otolaryngology), Yale University School ofMedicine New Haven, CT, USA, 3 Dept. of Food Science andTechnology, Oregon State University Corvallis, OR, USAContext effects in taste have generally been attributed to responsebiases rather than to sensory mechanisms intrinsic to tasteperception. Here we report evidence that extensive exposure tothreshold-level tastes appears to heighten the perception ofsuprathreshold tastes. We discovered the effect in a study ofindividual differences in threshold and suprathreshold sensitivityto sucrose and NaCl that involved measurement of 6, 2AFCdetection thresholds over 3 sessions, followed by a 4 th session inwhich intensity ratings were obtained for 12 suprathresholdstimuli using the gLMS. Under these conditions intensity ratingswere 2-3 times higher than in a preceding experiment thatincluded some of the same stimuli but no detection task. Analysisof data from 7 Ss who participated in both experiments confirmedthe differences were statistically significant (p