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umami solutions, and strongly avoid CaCl
2
. In contrast, littermate
controls with the BTBR/BTBR (BB) haplotype are indifferent to
sucrose, umami and CaCl
2
. These behavioral differences might be
mediated by several possible mechanisms, including gustatory or
post-ingestive. We therefore measured taste-evoked multi-unit
chorda tympani nerve responses in BN and BB mice, in order to
compare them on taste sensation more specifically. The BN mice
had higher responses to sucrose and the umami compound IMP
than did the BB mice. This suggests that differences in sweet and
umami taste perception, mediated by Itpr3, influence the strain
differences in behavioral preferences. Additional data will be
needed to compare the strains on responses to CaCl
2
and other
compounds. Acknowledgements: Funding provided by
NIH R01 DK-46791
#P26
POSTER SESSION I:
MULTIMODAL RECEPTION;
CHEMOSENSATION & DISEASE;
TASTE PERIPHERY; OLFACTION PERIPHERY
Taste-evoked chorda tympani responses in Fawn Hooded
Hypertensive and Brown Norway rats
Rachel M. Dana
1
, Chandra M. Cherukuri
1
, Michael G. Tordoff
2
,
Stuart A. McCaughey
1
1
Ball State University Muncie, IN, USA,
2
Monell Chemical Senses
Center Philadelphia, PA, USA
Recent studies have shown that Fawn Hooded Hypertensive (FHH)
and Brown Norway (BN) rat strains vary in their 2-bottle
preferences for ethanol, sucrose, CaCl
2
, and other taste solutions.
However, it is not known whether these strain differences in
behavior are due to differences in taste sensation or due to other
factors. We performed multiunit electrophysiological recordings
from the chorda tympani (CT) nerve in these two strains, in order
to examine whether these behavioral differences are associated
with variation in peripheral taste responsiveness. Rats were
anesthetized, the CT was accessed, and ethanol, sucrose, CaCl
2
and other solutions were flowed over the anterior tongue as we
measured the integrated whole-nerve activity. Taste-evoked
responses were of similar size in the strains, even for those
solutions on which they are known to differ behaviorally. These
data suggest that differences in non-gustatory mechanisms, or
possibly taste-related mechanisms in areas not innervated by the
CT nerve, are responsible for the previously observed strain
differences in 2-bottle preferences. Acknowledgements: Funding
provided by NIH R01 DC-10149
#P27
POSTER SESSION I:
MULTIMODAL RECEPTION;
CHEMOSENSATION & DISEASE;
TASTE PERIPHERY; OLFACTION PERIPHERY
CD36 Contributes to, but is not Required for, Fatty Acid
Transduction in the Taste System.
Han Xu, Douglas Holt, Timothy A. Gilbertson
Utah State University Logan, UT, USA
The scavenger receptor CD36 is expressed in a variety of tissues
where it is involved in multiple fat-related biological processes
including angiogenesis, atherosclerosis, inflammation and lipid
metabolism in mammals as well as in the detection of lipid-like
pheromones in insects. It is initially suggested involved in the
fatty acids gustatory detection with the immunocytochemical
identification in the taste cell apical membranes by Fukuwatari et
al. in 1997. Then evidences accumulated both in cellular and
behavior level (El-Yassimi et al. 2008; Sclafani et al. 2007 and
Laugerette et al. 2005) after the CD36-deficient mice were
generated. Nonetheless, the role of CD36 in fatty acid gustatory
detection, as a direct lipid sensor or as a protein that facilitates the
function of fatty acid-activated G protein coupled receptors, such as
GPR120 expressed in taste cells, remains to be determined. To
investigate this, we measured concentration-response functions for
the ability of fatty acids to activate cells using ratiometric calcium
imaging. Comparisons were made among cell lines expressing
GPR120 with or without CD36 or CD36 alone as well as taste
cells freshly isolated from CD36-deficient mice and wild type
mice. In both cases, the presence of CD36 caused a leftward shift
of the concentration-response function, which is consistent with the
facilitating ability of CD36 to fatty acid responsiveness. However,
taste cells lacking CD36 were still capable of responding to fatty
acids. At the behavioral level, we observed a reduced
responsiveness to linoleic acid in CD36-deficient mice after
formation of an aversion conditioned to the taste of linoleic acid.
These results suggest CD36 is not required but certainly contributes
to fatty acid responsive pathways in the taste system.
Acknowledgements: NIH grant DK059611 (to TAG) and
International Flavors & Fragrances.
#P28
POSTER SESSION I:
MULTIMODAL RECEPTION;
CHEMOSENSATION & DISEASE;
TASTE PERIPHERY; OLFACTION PERIPHERY
Medium chain fatty acid transduction in mouse taste cells
is TRPM5-independent
Yan Liu, Timothy A Gilbertson
Department of Biology, Utah State University Logan, UT, USA
Previous studies concluded that transient receptor potential channel
type M5 (TRPM5) plays a critical role in long chain fatty acid
transduction in mouse taste cells. Cellular responses to linoleic
acid in Type II cells, for example, occur in a qualitatively similar
fashion to sweet, bitter and umami stimuli (Liu et al.,
J Neurosci
31: 8634, 2011). We have previously shown that mice respond
behaviorally to other classes of fatty acids including medium chain
saturated fatty acids (C
8:0
-C
14:0
) and their taste cells respond to these
stimuli as well. However, the transduction mechanism underlying
these responses is unknown. We have used both cell-based and
behavioral assays to explore the mechanism of medium chain fatty
acid transduction in mouse taste cells and found that unlike the
case for the polyunsaturated fatty acids, this process is TRPM5-
independent. Using fura-2 based calcium imaging, we found that
lauric acid (C
12:0
) elicited a robust and reversible increase in
intracellular calcium in taste cells isolated from wild type mice and
similar responses, in terms of response magnitude, percentage of
responsive cells and concentration dependence, were seen in taste
cells from mice lacking TRPM5. These results suggest that TRPM5
is not involved in medium chain fatty acid transduction in mouse
taste. Currently we are investigating the behavioral responses to a
series of medium chain fatty acids in wild type and TRPM5
knockout mice. Thus, our preliminary data are consistent with the
interpretation that medium chain fatty acid transduction pathway is
significantly different than for the polyunsaturated fatty acids in
terms of its dependence upon TRPM5. The specific elements of the
pathway for medium chain fatty acid transduction remain to be
elucidated. Acknowledgements: Supported by NIH grant
R01DK059611
Abstracts | 37
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