1 1 Symposium Chemosensory Receptors Satellite DEVELOPMENT ...

433 Poster Central Taste and Chemosensory BehaviorA NEW METHOD OF ASSESSING TASTE QUALITYGENERALIZATION IN RATSGrobe C.L. 1 , Spector A.C. 1 1 Department of Psychology and Center forSmell and Taste, University of Florida, Gainesville, FLCurrently, taste generalization behavior in rats is assessed by usingthe conditioned taste aversion paradigm, which has some practicallimitations including concentration and extinction effects. We modifieda procedure from Morrison (1967) in which we trained 4 groups ofthirsty rats to lick one response spout after sampling (5 licks) arepresentative compound (standard stimulus) from one of 4 prototypicaltaste qualities (NaCl, sucrose, quinine HCl, citric acid) and to lickanother response spout after sampling any of the other 3 prototypicaltaste stimuli (comparison stimuli). Concentration of all compounds wasvaried to render intensity an irrelevant cue. Correct responses werereinforced with water and incorrect responses were punished with atime-out. Rats readily learned to discriminate the solutions representingthe putative 4 basic taste qualities from each other. We deliveredunreinforced/unpunished test trials on approximately 15% of the sessiontrials to identify how the trained animals would categorize the novelstimuli including new concentrations of the 4 standard compounds,mixtures of NaCl and sucrose, and water. Rats correctly classified thetest solutions. Although, surprisingly, when water was used as a teststimulus, the rats categorized it as quinine-like suggesting that theweakest concentration of quinine may have been too low (i.e., “waterlike”).We have now adapted the task to include water in the array ofcomparison stimuli. Soon, we will be poised to obtain profiles forseveral novel taste compounds. Supported by NIH grants F31-DC007301 [CLG] and R01-DC01628 [ACS].434 Poster Central Taste and Chemosensory BehaviorGENETIC INFLUENCES ON TASTE PREFERENCE FORETHANOLDishaw L.V. 1 , White T.L. 1 , Youngentob S.L. 2 1 Psychology, Le MoyneCollege, Syracuse, NY; 2 SUNY - Upstate Medical University, Syracuse,NYAlthough many factors contribute to alcoholism, the palatability of itstaste may facilitate initial ingestion. The taste of ethanol is a collectionof qualities, including sweet and bitter. Since individual variation in theperception of taste qualities is in part genetically determined, it might beanticipated that PROP sensitive individuals would consume less ethanoldue to its bitter quality. However, studies examining human PROPsensitivity and ethanol consumption have produced conflicting results,possibly due to the complex social factors surrounding ethanolingestion. The present study utilized mice to investigate the relationshipof bitter taste to ethanol ingestion. It was hypothesized that PROPsensitivity would predict ethanol preference. Four mouse strains(C57/BL6: Ethanol preferring, BALB/c: Ethanol avoiding, SWR/J:PROP sensitive, C3HeB/FeJ: PROP insensitive) were evaluated fortaste preferences (relative to water) for PROP and for ethanol with aBrief Access Taste Test in order to minimize post-ingestiveconsequences of the stimuli. Three of the four mouse strains supportedthe hypothesis. That is, as predicted, if sensitivity to PROP was low,ethanol preference was high (C57, C3HeB). Conversely, if sensitivity toPROP was high, ethanol preference was low (SWR). Only the BALB/cstrain showed a high lick ratio to PROP despite a low level ofpreference for ethanol. The basis for the latter result is unclear.Nonetheless, these findings suggest that bitter perception has a role inethanol preference. Supported by Le Moyne Research Funds (Studentand Research & Development) and NIAA RO1AA014871.435 Poster Central Taste and Chemosensory BehaviorBEHAVIORAL TESTING OF SALT TASTE SENSITIVITY INTRPV1 KNOCK-OUT MICETreesukosol Y. 1 , Spector A.C. 1 1 Department of Psychology & Centerfor Smell and Taste, University of Florida, Gainesville, FLCurrent evidence suggests salt taste transduction involves at least twomechanisms, one that is amiloride-sensitive (AS) and appears to utilizeapically located epithelial sodium channels relatively selective for Na +and a second that is amiloride-insensitive (AI) and utilizes non-specificcation channels. Electrophysiological recordings show that Trpv1knock-out mice lacking the vanilloid receptor-1 (VR-1) demonstrate noAI chorda tympani (CT) responses to NaCl suggesting that AI salt tastetransduction depends on the product of the Trpv1 gene (Lyall et al.,2004). To extend these findings into a functional context, we trainedTrpv1 knock-out (KO) and wild type (WT) C57BL/6J mice (n = 9-10/group) in a two response operant discrimination procedure to lick aresponse spout upon sampling from an array of NaCl concentrations andto lick another response spout upon sampling water. Mice were alsotested in sessions in which all solutions contained 100 µM amiloridehydrochloride. Correct responses were reinforced with water andincorrect responses were punished with a time-out. The mice were thentested with an array of KCl concentrations. Both the KO and WT micehad similar detection thresholds for NaCl and KCl. Amiloride shiftedthe NaCl sensitivity curve to the same degree in both groups and had noeffect on KCl thresholds. Thus, contrary to predictions based on CTrecordings, these findings suggest the VR-1 variant is not necessary fornormal taste detection of NaCl or KCl with or without 100 µMamiloride. Supported by NIH R01-DC04574.436 Poster Central Taste and Chemosensory BehaviorCYCLOHEXIMIDE: NO ORDINARY TASTE STIMULUSHettinger T.P. 1 , Formaker B.K. 1 , Frank M.E. 1 1 Oral Health &Diagnostic Sciences, UCONN Health Center, Farmington, CTRats and mice avoid cycloheximide, a focus of work on bitter taste(Boughter et al., 2005; Mueller et al., 2005), at concentrations muchlower than thresholds for most bitter stimuli. Hamsters, Mesocricetusauratus, also find this toxic antibiotic uniquely aversive; 2-bottleaversion thresholds approximated 1 µM (P < .001). Preference vs. waterfell from 36 ± 5% for 0.3 µM to 17 ± 6% for 3 µM cycloheximide. Likeother non-ionic stimuli avoided by hamsters (Frank et al., 2004), 1 mMcycloheximide did not activate the hamster chorda tympani (CT) nerve.A small consistent CT response was elicited to 10 mM cycloheximide(P = 0.004), a concentration 10,000 times higher than behavioralthreshold. Thus, hamsters´ aversions to 1 µM to 1 mM cycloheximideare not tied to CT responses. Given low behavioral thresholds, naïvehamsters, surprisingly, drank an average 1.5 mL of 0.5 mMcycloheximide, an amount near the rat LD 50 , when presented in a 1-bottle test. The cycloheximide did not kill them; however, they found itacceptable just once. When tested 2 days in a row or with as many as 21days intervening, the second intake averaged 21% of the first intake (P< 0.000001), demonstrating a persistent “acquired” aversion. Sources ofthe enhanced aversion are unknown but may involve induction ofreceptors or learned aversions. Rats, to which cycloheximide ismultisensory (Omura et al., 1961), learn odor aversions induced byintake of 0.4 mM cycloheximide (Fukuskima et al., 2002). Evidently,chemosensory properties of cycloheximide, nearly tasteless to humans,require further definition. [Supported by NIH grant DC04099]109