2009 Abstracts - Association for Chemoreception Sciences

classify subjects as PROP non-tasters, moderate tasters, orsupertasters. The classification of PROP tasters was determinedby comparing PROP taste intensity to edible taste strips thatcontained 140 nmoles of NaCl. Next, taste recognition thresholdsfor PROP were examined by the ascending limits method, and themethod of reversals. In our subject population (n = 100),approximately 80 percent of subjects could detect PROP as bitter.For PROP tasters, taste recognition thresholds spanned two logunits with an upper limit of 130 nmoles. These taste recognitionthresholds were over one order of magnitude lower than thosereported with aqueous tests. Subjects were then tested for theirability to detect PROP with their nasal passages occluded. Tasterecognition thresholds for half of the subject population wereidentical in both the absence and presence of nose clamps. Theremaining subjects detected PROP at the next higher or nextlower amount. Edible taste strip technology is a highly sensitiveand promising method for examining bitter taste function. Thesestrips readily identify taste blindness to PROP, and can identifymoderate tasters and supertasters. Future studies will correlatePROP taster status with genotype analysis of the TAS2R38 gene,and how the ability to detect PROP may affect overall bitter tastefunction.#P302 Poster session VII: Chemosensory Psychophysics IIB6 mice display confusion in behaviorally discriminatingbetween quinine and citric acidYada Treesukosol, Clare M Mathes, Alan C SpectorFlorida State University Tallahassee, FL, USAIn rodents, some taste-responsive neurons respond to bothquinine and acid stimuli. There is also evidence in the literaturesuggesting that, under certain circumstances, rodents display somedegree of difficulty in discriminating quinine and acidstimuli. Here, male C57BL/6J mice (n=10) were explicitly testedin a quinine vs. citric acid discrimination task. Water-restrictedmice were first trained in a two response-operant discriminationprocedure to lick a response spout upon sampling from an arrayof sucrose concentrations and to lick another response spout uponsampling from an array of citric acid concentrations. Correctresponses were reinforced with water and incorrect responseswere punished with a time-out. The mice were then tested fortheir ability to discriminate between other pairs of tastestimuli. Mice had severe difficulty discriminating citric acid fromquinine and 6-n-propylthiouracil (PROP) with performanceslightly, but significantly, above chance. In contrast, mice wereable to competently discriminate sucrose from citric acid, NaCl,quinine and PROP. In another experiment, mice that wereconditioned to avoid quinine by pairings with LiCl injections(n=8), subsequently suppressed licking responses to quinine andcitric acid and, to a lesser extent, NaCl, but not to sucrose in abrief-access test (25 min session, 5 s trials) relative to NaClinjectedcontrol animals (n=7). However, mice that wereconditioned to avoid citric acid significantly suppressedlicking only to that stimulus compared with controls(n=8/group). Collectively, the findings from these experimentssuggest that in mice, citric acid and quinine substantially sharechemosensory features making discrimination difficult butare not perceptually identical.#P303 Poster session VII: Chemosensory Psychophysics IINon synomymous SNPs in human tas1r1, tas1r3, mGluR1 andindividual taste sensitivity to glutamateMariam Raliou 1,2 , Anna Wiencis 2 , Anne-Marie Pillias 1 , AurorePlanchais 1 , Corinne Eloit 1,3 , Yves Boucher 4 , Didier Trotier 1 ,Jean-Pierre Montmayeur 2 , Annick Faurion 11NBS-NOPA, INRA Jouy-en-Josas, France, 2 CESG-CNRS Dijon,France, 3 Dept ORL Hôpital Lariboisière Paris, France, 4 FacultéDentaire, UFR Ondotologie Paris, FranceHuman subjects show different taste sensitivities to monosodiumglutamate (MSG), some of them being unable to detect thepresence of glutamate. Our objective was to study possiblerelationships between non-synonymous single nucleotidepolymorphisms (nsSNP) in human tas1r1, tas1r3, as well as otherputative receptor coding genes (mGluR4 and mGluR1), and thetaste sensitivity of each subject to glutamate. The sensitivity wasmeasured using a battery of tests to distinguish the effect ofsodium ions from the effect of glutamate ions in monosodiumglutamate. A total of 142 genetically unrelated Caucasian Frenchsubjects were considered: 27 non tasters to glutamate (specificageusia), 21 hypo-tasters and 94 tasters. Expression of tas1r1 andtas1r3 was tested on fungiform papillae by RT-PCR on a sampleof subjects from all groups. nsSNPs were determined by genomicDNA sequencing. The frequency of the mutations was comparedacross subject groups. All subjects, including those presenting aspecific ageusia for glutamate, expressed the candidateheterodimeric receptor Tas1R1-Tas1R3. Ten nsSNPs wereidentified in tas1r1 (n=3), tas1r3 (n=3) and mGluR1 (n=4) genes.mGluR4 only showed 3 silent SNPs. Two mutations -C329T intas1r1 and C2269T in tas1r3- were significantly more frequent innon tasters compared to tasters whereas G1114A in tas1r1 wasmore frequent in tasters. Other nsSNPs including T2977C inmGluR1 and more rare nsSNPs are also involved but, using thesethree genes, a part of the interindividual variance remainsunexplained. Some of the nsSNPs reported here can partly explainthe observed individual differences of sensitivity to glutamate andthe taste of glutamate may involve also other receptors than thoseconsidered here.#P304 Poster session VII: Chemosensory Psychophysics IIUnderstanding the Relationship Between Saltiness and UmamiChristopher T. Simons, Kelly AlbinGivaudan Flavors Corp., Science & Technology Cincinnati,OH, USANaCl and MSG evoke sensations that humans recognize as saltyand umami, respectively. However, sensorially the relationshipbetween salt and umami is complex as most foods contain bothNaCl and umami compounds and the prototypical umamistimulus, MSG, includes Na+. Herein we sought to determinehow perceived salt and umami intensities change as (A) NaCl isheld constant and MSG concentrations vary and (B) MSG is heldconstant and NaCl concentrations vary. In each experiment,panelists were asked to rank aqueous mixtures of NaCl and MSGat varying concentrations according to perceived saltiness and/orumami intensity. As expected in exp 1, increasing MSG whileholding the NaCl concentration constant resulted in greaterperceived umami intensity. Similarly, as MSG levels increased,perceived saltiness increased. In exp 2, adding salt to a constantlevel of MSG increased perceived saltiness but had no effect onP O S T E R SAbstracts | 121