2009 Abstracts - Association for Chemoreception Sciences

Chorda tympani (CT) anesthesia leads to elevatedglossopharyngeal (IX) sensation; among supertasters of 6-npropylthiouracil,it also enhances trigeminal (V) sensation. Thesefindings imply that oral disinhibition occurs in proportion togenetic taste status, and that affected sensations are differentiallysusceptible to these effects. Supporting this idea, in healthysubjects with low taste function, unilateral anesthesia of either thelingual nerve (i.e., CT and V; N = 46) or the chorda tympani (N =28) asymmetrically compromises posterior taste sensation, withthe side contralateral to anesthesia showing the least suppression.Lingual nerve block produced posterior asymmetry for all fourcommon taste modalities, but direct CT block did so only forsalty stimuli. Previous reports suggest that loss of 2+ oral sensoryinputs broadly compromises taste function; these reports alsoshow posterior taste enhancement with CT block, but modalityspecificasymmetry may represent mild disinhibition inindividuals with low native taste function. Finally, contralateralanterior oral burn remained intact with both nerve blocks, whileposterior oral burn was blunted bilaterally; these data imply thatdisinhibitory trigeminal enhancement is associated with hightaster status. In sum, disinhibitory effects of localized oral sensoryloss vary based on genetic taste status; posterior taste elevationmanifests in nontasters as asymmetric loss, while trigeminaleffects occur mainly in supertasters.#8 Withdrawn#9 Gustation“Restrained Eaters” Show Abnormal and DifferentialfMRI Activation to Sucrose and SaccharinClaire Murphy 1,2 , Nobuko Kemmotsu 1,21San Diego State University San Diego, CA, USA,2University of California, San Diego San Diego, CA, USAObesity in the US has reached epidemic proportions, affectingpresent and future health status of millions of Americans. Personswho exercise cognitive restraint over eating behavior may provideinsights into underlying mechanisms of obesity. “Restrainedeaters” attempt to control weight by cognitive restraint, activelyregulating the quantity and quality of food intake. Whether theyhave altered brain activity to nutritive and non -nutritive tastestimuli is unknown. The present study investigated tasteinformation processing in the central nervous system using thefunctional MRI technique. Sixteen participants were “restrainedeaters” defined by Factor 1 (cognitive restraint) items of the ThreeFactor Eating Questionnaire (TFEQ; Stunkard & Messick, 1985),and 16 were “non-restrained eaters.” The BOLD signal changewas investigated when the participants were hungry and satiatedwith a nutritional preload, in response to sucrose and saccharin.Non-restrained eaters responded with more robust activation tothe caloric sweetener. In contrast, the restrained eaters showed adifferent activation pattern, demonstrating greater response tosaccharin than to sucrose. Interestingly, restrained eaters showeddecreased activation in OFC and amygdala in response to thesaccharin when satiated, the same pattern observed in thenon-restrained eaters in response to sucrose. This differentialactivation to sucrose and saccharin, particularly in reward areas ofthe brain, suggests altered brain mechanisms in restrained eaters.A better understanding of the development and maintenance ofthis phenomenon may lead to strategies for prevention of andinterventions for obesity.#10 Gender effects on olfactory processingAxons of gustatory receptor 32a expressing neurons extendtheir terminal throughout adult lifetimeTetsuya Miyamoto, Hubert AmreinDepartment of Molecular Genetics and Microbiology,Duke University Medical CenterCourtship is an essential behavior for successful mating. In maleDrosophila, chemosensory cues are thought to control manyaspects of courtship such as identification of partners of the samespecies, appropriate sex and suitable mating status. Recently,we report that the gustatory receptor (Gr) gene, Gr32a, plays animportant role in male courtship. Gr32a mutant males shownormal courtship towards females. However, the courtship indexof Gr32a mutant males towards males and mated females, whichcontain male pheromones, is much higher than that of wild typemales. These results indicate that Gr32a is essential for detectionof a male inhibitory pheromone, which is necessary forsuppression of courtship towards unrewarding potential mates.Gr32a is expressed in chemosensory neurons of labial palp andlegs, but leg neurons are sufficient to repress male-male courtship.All gustatory neurons are thought to project to the primary tasteprocessingcenter, subesophageal ganglion. However, weoccasionally observed that Gr32a leg neurons directly project tothe ventro-lateral protocerebrum, which is known as a higherorder brain structure as receiving input from multiple sensorymodalities, including visual, auditory, and possibly olfactorycues. The morphology of Gr32a neurons outside of thesubesophageal ganglion shows a huge diversity among individualand even in either side of the same brain. Their axon ends atvarious positions, from the subesophageal ganglion to upper endof the ventro-lateral protocerebrum. The number of axon terminalis also widely ranged, from 1 to 20. Strikingly, there is a clearcorrelation among the probability of axon to reach the ventrolateralprotocerebrum, the complexity of axon terminal and age upto 60 days after eclosion. This is also observed in flies kept inisolation, though less significant than that of flies kept in a group.Our studies suggest Gr32a leg neurons slowly extend theirterminals throughout adult lifetime; this phenomenon might leadolder, socially experienced flies tend to avoid males and matedfemales more strictly.#11 Gender effects on olfactory processingRecognition of Sexual Cues in the Urine byMouse Vomeronasal OrganRon Yu 1,2 , Jie He 1 , Limei Ma 1 , Sangseong Kim 1 , Junichi Nakai 31Stowers Institute Kansas City, MO, USA, 2 University of KansasMedical Center Kansas City, KS, USA, 3 RIKEN Brain InstituteWako-shi, JapanThe vomeronasal organs of the mammalian species detect complexchemical signals in the urine that convey information about sex,strain, as well as the social and reproductive status of anindividual. How such complex signals are recognized by thevomeronasal organ is not well understood. In this study, we havedeveloped transgenic mice expressing the calcium indicator,G-CaMP2, to analyze the population response of vomeronasalneurons to urine from individual animals. We found that asubstantial portion of the cells were activated by either male urineor female urine, but most of them contributed little to sexdiscrimination. Sex information was represented by a surprisinglyAbstracts | 9