1 1 Symposium Chemosensory Receptors Satellite DEVELOPMENT ...

429 Poster Central Taste and Chemosensory BehaviorSHORT-TERM LICKING BY POTASSIUM-DEPRIVED RATSGuenthner C. 1 , McCaughey S. 2 , Tordoff M. 2 , Baird J.P. 3 1 Psychology &Neuroscience, Amherst College, Amherst, MA; 2 Monell ChemicalSenses Center, Philadelphia, PA; 3 Psychology, Amherst College,Amherst, MAPotassium-deprived rats have elevated intakes of KCl relative toreplete animals. It is not known, though, whether this appetite dependson learning about the post-ingestive consequences of tastant samples.To investigate the contribution of learned versus unlearned cues topotassium appetite, we tested eight potassium-deprived and eightcontrol rats for on their short-term intake. Animals were trained to lickfor water after fluid deprivation. They were then given brief-access tests(20s per solution) to lick for a diverse array of taste stimuli.Measurement of plasma potassium levels and a 24-h two-bottle test withKCl and water at the end of the experiment confirmed that thepotassium-deprivation treatment was effective at inducing potassiumdeficiency. Deprived rats drank less water and 10 mM citric acid in thebrief-access tests than did replete rats, but intakes of 200 mM KCl, 200mM NaCl, 100 mM CaCl2, and 100 mM MgCl2 were significantlygreater (p < 0.05) in the deprived group. The results suggest thatpotassium deprivation inhibits thirst in rats, but that it also induces anappetite that generalizes across several mineral solutions. The briefperiods of access precluded post-ingestive learning, and therefore themineral appetite must have been guided solely by unlearned factors,such as taste. Supported by a Howard Hughes Medical Institutefellowship to CJG.430 Poster Central Taste and Chemosensory BehaviorDISCRIMINATION AND POST-INGESTIVE EFFECTS INTRPM5 -/- MICEDe Araujo I.E. 1 , Riofrio A. 1 , Nicolelis M.A. 1 , Simon S.A. 21 Neurobiology, Duke University, Durham, NC; 2 Anesthesiology, DukeUniversity, Durham, NCMice lacking functional TRPM5 channels (TRPM5 -/- ) do not detectsweet (sucrose) and bitter (quinine) tastants. A comparison of thebehavior and electrophysiological responses of male TRPM5 -/- micepermit the investigation of two issues relevant to gustatoryphysiologists. The first is whether they can detect bitter tastants (e.g.nicotine) using sensory inputs other than taste, and the second iswhether they can distinguish the post-ingestive effects of sucrose andwater independently of taste. Preliminary results with a two-bottlepreference test suggest that TRPM5 -/- mice do discriminate between 1mM nicotine and water as well as between 1 mM nicotine and 10mMquinine (= water). We suggest that TRPM5 -/- mice use oralsomatosensory input to detect nicotine. Regarding post-ingestiveeffects, food and water-deprived TRPM5 -/- mice were given daily 30min free access to either water or 0.4M sucrose from one of two sippertubes while access to the other tube is blocked. This procedurealternates access to either solution for 6 consecutive days followed bypreference testing sessions where animals are given free access to bothtubes simultaneously. We found that in comparison to pre-conditioningpreference tests, TRPM5 -/- mice develop a preference to the tubepreviously associated with sucrose, suggesting that post-ingestivereinforcing properties of sucrose that are independent of taste mediatethis learning process. In both experiments related recordings will bepresented. Supported by DC-01065 and Philip Morris USA and PhilipMorris International.431 Poster Central Taste and Chemosensory BehaviorBEHAVIORAL ANALYSIS OF THE TASTE OF L-AMINOACIDS IN MICEMurata Y. 1 , Bachmanov A.A. 2 , Beauchamp G. 2 1 National ResearchInstitute of Fisheries Science, Yokohama, Kanagawa, Japan; 2 MonellChemical Senses Center, Philadelphia, PARecent studies showed that the mouse T1R1+T1R3 receptor isbroadly tuned to respond to L-amino acids when it is heterologouslyexpressed in vitro (Nelson et. al., 2002). Activation of the same tastereceptor suggests that L-amino acids share the same taste quality, whichcontradicts mouse behavioral data showing that taste qualities of L-amino acids are not identical. In order to investigate this apparentcontradiction, we examined taste quality perception of three L-aminoacids at concentrations that activate T1R1+T1R3 receptor in vitro: 50mM L-serine (Ser), 50 mM L-methionine (Met), and 50 mM L-glutamate (Glu) (Nelson et. al., 2002). Separate groups of C57BL/6Jmice were exposed to Ser, Met, Glu (presented as a mixture of 50 mMMSG, 2.5 mM IMP and 30 µM amiloride added to block sodium taste)or water (control) and injected with LiCl to form a conditioned tasteaversion (CTA). Mice were presented with each of the three L-aminoacid stimuli, and four basic taste solutions. An aversion to Sergeneralized to both Met and Glu, and also to Sucrose. However anaversion to both Met and Glu did not generalize to any of the stimulitested. Generalization of CTA from Ser to Met and Glu suggests thatconsistent with in vitro predictions, these amino acids elicit identicaltaste sensation in mice. However, our results also suggest that each ofthese L-amino acid stimuli have additional unique sensory qualities.For example, Ser evokes a sucrose-like taste that Met and Glu lack.Why CTA does not reciprocally generalize from Met and Glu to Serrequires further investigation. Supported by Fisheries Research Agency(Yokohama, Japan) Research Overseas Program (YM), AjinomotoAmino Acid Research Program grant (AAB) and NIH grant DC 00882(GKB).432 Poster Central Taste and Chemosensory BehaviorA HIGH-THROUGHPUT METHOD TO MEASURE NACLDETECTION THRESHOLD IN MICEIshiwatari Y. 1 , Beauchamp G.K. 2 , Bachmanov A.A. 2 1 Ajinomoto Co.,Inc., Kawasaki, Japan; 2 Monell Chemical Senses Center, Philadelphia,PACurrently known procedures to measure taste detection thresholds arenot suitable for high-throughput genetic studies due to their harmfulaspects or complexity of training. We have developed a simpleprocedure to measure NaCl detection threshold using conditioned tasteaversion and two bottle preference tests. First, we compared threeconditioning procedures, all followed by 48-h two-bottle tests: (a)presenting water-deprived mice with a single NaCl concentrationfollowed by LiCl injection (multiple groups were tested with differentconcentrations); (b) presenting each water-deprived mouse with threeNaCl concentrations near expected detection threshold, followed byLiCl injection; (c) presenting water replete mice with 150 mM LiCl for24 h. Mice that consumed LiCl started avoiding NaCl at lowerconcentrations than did LiCl-injected mice. Next, we altered tasteintensity and toxicity of consumed LiCl by changing LiCl concentrationor adding NaCl to LiCl and concluded that 150 mM LiCl is the optimalstimulus for conditioning. Finally, we compared sensitivity of 48-h and30-min tests for detecting thresholds in mice conditioned by LiClconsumption and found that the 48-h test is more sensitive. We haveconcluded that ingestion of 150 mM LiCl followed by the 48-h tests ofascending NaCl concentrations is the most efficient and sensitivemethod suitable for high-throughput genetic studies.108