Abstracts - Association for Chemoreception Sciences

(GL) of adult rats that underwent either unilateral neoCTX or
a control surgery at five days of age. Nerve activity following
application of various concentrations of NH 4
Cl, NaCl, and
sucrose was recorded using 0.5M NH 4
Cl and 0.5M KCl as
standards. There were no differences in nerve response to NH 4
Cl
or NaCl, but there was a significant difference for sucrose, with
neoCTX rats having higher GL responses to the tastant. Since
NH 4
Cl responses did not differ between surgical groups, there
may be differences following neoCTX in greater superficial
petrosal or superior laryngeal nerve activity, or alterations in
central processing which can account for the increase in NH 4
Cl
preference. Alternatively, the functioning of the GL may be more
affected following bilateral compared to unilateral neoCTX. The
mechanisms which lead to the observed injury-induced alteration
in sucrose responding are unknown. However, this increase in
responding following neoCTX could help explain observations
from the human literature in which early chorda tympani
damage is correlated with an increased preference for sugary
foods. Work is currently underway to record GL responses from
adult rats receiving bilateral neoCTX at 10 days of age.
#P159 POSTER SESSION III:
TRIGEMINAL; HUMAN OLFACTORY
PSYCHOPHYSICS; TASTE PERIPHERY
Mouse bitter taste
Wolfgang Meyerhof 1 , Kristina Lossow 1 , Hübner Sandra 1 ,
Frenzel Sabine 1 , Masataka Narukawa 1 , Anja Voigt 1 , Ulrich Boehm 2 ,
Jonas Töle 1 , Maik Behrens 1
1
German Institute of Human Nutrition Potsdam-Rehbruecke,
Department of Molecular Genetics Nuthetal, Germany, 2 University
of Saarland, School of Medicine, Department of Pharmacology and
Toxicology Homburg, Germany
extents. Behavioral experiments showed that these mice exhibit
diminished avoidance of several bitter compounds, whereas they
are indistinguishable from control mice in their avoidance of
denatonium benzoate. Together the data demonstrate that bitter
sensing cells are functionally polymorphic forming the basis for
variable behavioral responses to different bitter chemicals.
#P160 POSTER SESSION III:
TRIGEMINAL; HUMAN OLFACTORY
PSYCHOPHYSICS; TASTE PERIPHERY
Behavioral responses to trimethylamine -N -oxide using
the CTA paradigm in C57BL/6 mice
Yuko Murata, Meiko Kimura
Fisheries Research Agency Yokohama, Japan
Trimethylamine-N-oxide (TMAO) is a common and compatible
osmolyte in tissues of marine organisms, and counteracts
the effects of protein destabilizing agents such as urea in
elasmobranches. Gadoid fish, elasmobranches and scallop have
high levels of TMAO in their muscles. TMAO is thought to
contribute to the taste of these fishes but the taste of TMAO is
unclear. In this study, we investigated taste quality perception
of TMAO in C57BL/6 mice using conditioned taste aversion
(CTA) experiments.We developed LiCl-induced CTA to 1.0%
TMAO and examined its generalization to 12 taste stimuli.
CTA to TMAO significantly generalized to D-phenylalanine,
saccharine and quinine. These results suggest that mice avoid
the taste of TMAO and its taste perception in mice is similar
to D-phenylalanine, saccharin and quinine. We will also
present behavioral thresholds and behavioral response to low
concentration (below 0.1%) of TMAO.
Depending on dose, bitter chemicals can be toxic or healthy.
Accordingly, consumers like some bitter tasting foods while
they avoid others. For a detailed understanding of bitter taste
physiology we examined the receptors for bitter substances and
their cells in mice. Functional expression analysis showed that
mice and humans detect a similar range of bitter compounds
even though mice possess 30% more Tas2r bitter taste receptor
genes than humans. Intriguingly, recognition of bitter chemicals
in the two species is mostly evoked by non-orthologous Tas2rs.
Based on the number of cognate compounds, mouse Tas2rs,
like their human counterparts, can be classified in generalists,
moderately tuned receptors and specialists. However, compared
with humans, mice seem to possess a larger fraction of specialists
suggesting that a greater number of Tas2r genes offers the luxury
of a set of specific receptors for selected bitter compounds.
Genetic labeling and in situ hybridization experiments revealed
that mice possess 2200 to 3300 bitter-sensing cells. They express
the entire repertoire of Tas2r genes at individual levels and
in limited subsets. Accordingly, genetic ablation of the cells
expressing one Tas2r, i.e., Tas2r131, did not extinguish the entire
population of bitter sensing cells but only ~50%. The remaining
bitter sensing cells displayed complete absence of some
Tas2rs, whereas expression of others was reduced to different
#P161 POSTER SESSION III:
TRIGEMINAL; HUMAN OLFACTORY
PSYCHOPHYSICS; TASTE PERIPHERY
Purification, biophysical characterization and first
crystallization trials of the ligand-binding domain
of the human T1R3 sweet taste receptor.
Fabrice Neiers, Maud Sigoillot, Elodie Maîtrepierre, Christine Belloir,
Nicolas Poirier, Loïc Briand
Centre des Sciences du Goût et de l’Alimentation, INRA CNRS
Université de Bourgogne Dijon, France
The heterodimeric T1R2/T1R3 sweet taste receptor is
composed of two class C G-protein coupled receptors
(GPCRs), while T1R1/T1R3 heterodimer is involved in umami
taste perception. Class C GPCRs share common structural
homologies including a large N-terminal domain (NTD) linked
to the seven transmembrane domain by a cysteine rich region.
T1R2- and T1R1-NTDs have been shown to contain the primary
binding site for most of the sweet ligands and umami tastants,
respectively. In contrast, the contribution of T1R3-NTD to sweet
and umami compound detection is less documented. The human
T1R3-NTD was produced in Escherichia coli using a strategy
recently described (Maîtrepierre et al., Protein Expr. Purif., 2011).
POSTER PRESENTATIONS
Abstracts are printed as submitted by the author(s).
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