1 1 Symposium Chemosensory Receptors Satellite DEVELOPMENT ...

81 Poster Peripheral Olfaction and Peripheral TasteSYNAPTOTAGMIN-1-LIKE IMMUNOREACTIVITY INCIRCUMVALLATE TASTE BUDS OF THE RATThomas S. 1 , Yang R. 1 , Ma H. 1 , Kinnamon J.C. 1 1 Biological Sciences,University of Denver, Denver, COSynaptotagmin (syt) is a vesicle associated glycoprotein ofneurosecretory granules and synaptic vesicles. Synaptotagmin has twoC2 domains that interact with Ca 2+ and is thought to be the primarysensor for synaptic vesicle fusion and neurotransmitter exocytosis. Weused immunocytochemistry with syt-1 and other known functionalmarkers in taste cells to learn if synaptotagmin is associated with tastecells thought to possess synapses. Preliminary results reveal that syt-1 ispresent in a small subset of taste cells and nerve processes in ratcircumvallate taste buds. Approximately 13% of taste cells display syt-1-like immunoreactivity (LIR). The immunoreactive taste cells areslender in shape and extend the entire height of the taste bud from basallamina to taste pore. Syt-1-LIR colocalizes with synaptobrevin-2-,protein gene product 9.5 (PGP 9.5)-, and serotonin-LIR in a subset oftaste cells, however, syt-1-LIR taste cells do not contain α-gustducin orPLCβ2 which are believed to be present in type II taste cells. Inaddition, we used DAB immunoelectron microscopy and found that syt-1-LIR taste cells possess synapses onto nerve processes in ratcircumvallate taste buds. These data suggest that syt-1 is present in typeIII taste cells and is associated with synapses onto nerve processes.Supported in part by NIH grant DC00285.82 Poster Peripheral Olfaction and Peripheral TasteCHARACTERISTICS OF GUSTATORY RESPONSES FROMTHE SOFT PALATE IN C57BL MICEHarada S. 1 , Ooki M. 1 , Nakayama A. 1 , Miura H. 1 1 Oral Physiology,Kagoshima University, Kagoshima, JapanGustatory responses from the soft palate in C57BL mice were studiedby electrophysiological and behavioral experiments. Integrated tasteresponses from the greater superficial petrosal nerve (GSP), innervatingthe soft palate, to NaCl, HCl, sucrose (Suc), quinine HCl (QHCl), andother taste substances at various concentrations were recorded.Threshold for QHCl was 0.00001 M and QHCl produced robust phasicand tonic responses at 0.01 M. Threshold for HCl was 0.0003 M androbust phasic and tonic responses were observed at 0.01 M. Thresholdfor Suc response was rather high at 0.03 M and the response magnitudeincreased abruptly with increasing concentration until 1 M. Artificialsweeteners tested (0.1 M aceslfame-K, 0.1 M sucralose, 0.02 Msaccharin) also produced large responses similar to 1 M Suc.Stimulatory effectiveness for NaCl was smaller than that in the chordatympani (CT). Although inhibitory effects of amiloride on responses toNa salts was weak in the rat GSP, 50 µM amiloride strongly inhibitedtonic responses to NaCl and Na-acetate in mice GSP similarly to that inthe CT. To determine the relative importance of the three major nerves[the GSP, the glossopharyngeal (GL), and the CT] for mediating tasteinformation, effects on licking behavior by bilateral transection of eachnerve or combination of the nerves in mice were studied. As for theQHCl, the effect of GSP + GL transection was large by ~75%. Theseresults suggest functional differences of soft palate taste buds amongrodents.83 Poster Peripheral Olfaction and Peripheral TasteMIXING SWEET AND SOUR STIMULI: EFFECTS ON THEHAMSTER CHORDA TYMPANILin H. 1 , Formaker B.K. 1 , Hettinger T.P. 1 , Frank M.E. 1 1 Oral Health &Diagnostic Sciences, UConn Health Center, Farmington, CTChorda tympani (CT) and central hamster taste responses to sucroseare inhibited by quinine•HCl when presented together in a mixture; inaddition, central sucrose responses are also inhibited by mixtures withcitric acid (HCit) [Formaker & Frank, 1996; Vogt & Smith, 1993a, b].Thus, we hypothesized that mixtures of sucrose with acids wouldreduce sucrose CT responses. We recorded CT responses in a total of 11golden hamsters (Mesocricetus auratus) to the following stimuli: 3mMHCl, 10mM HCit, 10mM acetic acid (HAc), 100mM sucrose and thebinary combinations of sucrose with each acid. Responses to 500 mMNH 4 Cl were used to normalize response measurements. Responses tosucrose mixtures with HCit equaled responses to HCit alone and weresmaller (p < 0.001) than responses predicted by an additive responsemodel, implying sucrose response suppression by HCit. In contrast,responses to sucrose mixtures with HAc or HCl were larger thanresponses to either mixture component alone (p < 0.001) and equaledresponses predicted by an additive response model, implying responseindependence. Solution pH did not account for these effects. We alsorecorded CT responses to a concentration series of HCit (1, 3, 10mM)alone and mixed with 100 mM sucrose in 4 animals. As with HAc andHCl, responses to mixtures with 1mM HCit were larger than responsesto either mixture component presented alone (p < 0.001); however, themixture response was still smaller (p < 0.05) than that predicted by anindependent response model. Thus, HCit may modulate the sucrosereceptor complex making it less effective. Alternatively, cross-talk mayoccur between the sweet and sour stimulus modalities in the hamstergustatory periphery. [Supported by NIH grant DC 040499]84 Poster Peripheral Olfaction and Peripheral TasteAMILORIDE INHIBITION OF THE NA-EVOKED LINGUALSURFACE POTENTIALS (LSP) VARIES IN HUMANSFeldman G. 1 , Heck G. 2 1 Internal Medicine, Virginia CommonwealthUniversity, Richmond, VA; 2 Physiology, Virginia CommonwealthUniversity, Richmond, VAAs we previously reported Na affects the LSP in humans, and insome people the Na-evoked LSP is partly inhibited by amiloride, ablocker of the epithelial Na channel. In this study we examined whetherthe amiloride effect is constant in given individuals or whether it variesfrom one day to the next. Using a voltage sensing gustometer adheringto the anterior surface of the tongue, the amiloride effect was measuredas 150 mM NaCl superfused the lingual surface. The amiloride effectwas quantified as the induced rate of change of the LSP (mV / sec);larger positive numbers signify greater effects. In 10 subjects, 100 µMamiloride inhibited the Na-evoked LSP an average of 0.0280 (±0.049SD). When the same subject was tested repeatedly on different days theamiloride effect varied considerably. For example, in one subjectamiloride´s effects were determined on 13 days; the average effect was0.155, the minimum was 0.020 and the maximum was 0.357. In anothersubject amiloride´s effects were determined on 5 days; the average was-0.003, the minimum was -0.025, and the maximum was 0.041. Thesedata demonstrate that the amiloride effect on the Na-evoked LSP variesamong subjects and that in individual subjects the amiloride effectvaries from one day to the next. Daily variation of the amiloride effectcould suggest that the Na-evoked LSP is responding to physiologicalregulatory events, such as hormones. If this speculation is correct, thenit is possible that in humans the perception of salt taste may also vary inresponse to physiological events. This work is funded by a MeritReview Grant from the Department of Veterans Affairs.21