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#P249
POSTER SESSION VI:
OLFACTION CNS; TASTE PERIPHERY &
CNS; MULTIMODAL RECEPTION
Effect of Leptin on Neurons of the Rostral Nucleus of the
Solitary Tract and Potential Roles for Primary Cilia
Min Wang
1
, Charlotte M Mistretta
1
, Robert M Bradley
1,2
1
University of Michigan/School of Dentistry/Department of
Biologic and Materials Sciences Ann Arbor, MI, USA,
2
University
of Michigan/School of Medicine/Department of Molecular and
Integrative Physiology Ann Arbor, MI, USA
Leptin, secreted by adipocytes, acts on CNS neurons to modulate
energy balance. For example, in the hypothalamus ciliated neurons
respond to circulating leptin to produce melanocyte-stimulating
hormone which inhibits feeding. Because the rostral nucleus of the
solitary tract (rNST) is a critical brainstem nucleus that processes
gustatory signals important in feeding, we investigated: location
and number of ciliated neurons in rNST; presence of receptors
associated with feeding effects of leptin in rNST; colocalization of
leptin receptors and cilia in rNST neurons; and, responses to leptin
in rNST neurons. Cilia are present on the majority of adult mouse
and rat rNST neurons and rNST cilia stain positively for
somatostatin receptor 3 and melanin concentrating receptor 1, both
known to be important in feeding control. In addition, the leptin
receptor OB-Rb colocalized with rNST cilia. The effect of leptin on
biophysical properties of rNST neurons was examined using patch-
clamp recording in horizontal brain slices. Bath application of
leptin (100 nM) resulted in membrane hyperpolarization in 40% of
rNST neurons tested, depolarization in a further 5%, and no effect
in the remaining neurons. Leptin inhibited the frequency of
depolarization-induced action potentials in 55% of rNST neurons
but did not alter the amplitude of excitatory postsynaptic currents
initiated by stimulation of the solitary tract. Superfusion of TTX,
and the synaptic blockers CNQX, APV and bicuculline had no
effect on leptin initiated changes in membrane potential
demonstrating that leptin did not influence synaptic transmission.
The results suggest that leptin might act on receptors on rNST
neuronal cilia to modulate transmission of taste initiated signals to
higher brain centers important in the control of feeding behavior.
Acknowledgements: NIH NIDCD Grant DC000288
#P250
POSTER SESSION VI:
OLFACTION CNS; TASTE PERIPHERY &
CNS; MULTIMODAL RECEPTION
Retronasal Olfaction/Taste (Volatiles/Sweetness) Interactions
in Tomatoes
Linda M. Bartoshuk
1,2
, Adilia Blandon
2
, David G. Clark
2
,
Thomas A. Colquhoun
2
, Sonia Hudson
2
, Harry J. Klee
2
,
Howard K. Moskowitz
2,3
, Charles A. Sims
2
, Derek J. Snyder
1,2,4
,
Denise M. Tieman
2
1
University of Florida/Center for Smell and Taste Gainesville,
FL, USA,
2
University of Florida/Plant Innovation Program
Gainesville, FL, USA,
3
Moskowitz-Jacobs White Plains, NY, USA,
4
San Diego State University San Diego, CA, USA
Interactions between retronasal olfaction and taste have been of
interest for many years for practical as well as theoretical reasons.
The mechanisms underlying these interactions are not well
understood and indeed, multiple factors are likely involved. We
have been particularly interested in altering retronasal olfaction by
removing taste (e.g., anesthesia, gymnema sylvestre). Most
recently, we have begun to study the contributions of retronasal
olfaction to taste in natural products. Tomatoes with known
chemical variation were grown at the University of Florida. Sugars
as well as 61 volatiles were chemically assessed and sensory
characteristics (including sweetness and flavor intensity) were
psychophysically assessed. Multiple regression showed that flavor
made a contribution to sweetness that was independent of the
contribution associated with sugars (p<.0001). Evaluation of each
volatile showed that 7 of the 61 made contributions to sweetness
that were independent of those made by sugars (at least p<.05).
Those volatiles were neral (lemon), 4-carene (woody, sage, thyme),
1-nitro-2-phenylethane (cinnamon), isopentyl acetate (juicy fruit,
banana), 3-methyl-1-butanol (whiskey), 6-methyl-5-hepten-2-ol
(green, coriander), isovaleric acid (cheesy, sweaty). One of the
attributes of retronasal olfaction/taste interactions that has been
considered is the “congruence” of the odorant and tastant.
“Congruence” is roughly defined to mean the degree to which the
two are commonly experienced together (e.g., orange and sweet).
Some of the tomato volatiles noted above are congruent with sweet
but others are not (4-carene, 6-methyl-5-hepten-2-ol, isovaleric
acid). Further studies like this using natural products may lead to
new insights about the rules governing retronasal olfaction/taste
interactions. Acknowledgements: University of Florida Research
Foundation, Florida Agricultural Experiment Station
#P251
POSTER SESSION VI:
OLFACTION CNS; TASTE PERIPHERY &
CNS; MULTIMODAL RECEPTION
The effects of stimulus intensity on retronasal odor
enhancement by taste
Tomomi Fujimaru
1
, Nicole Babb
1, 2
, Barry Green
2
, Juyun Lim
1
1
Oregon State University, Department of Food Science Corvallis,
OR, USA,
2
The John B. Pierce Laboratory New Haven, CT, USA
It was recently reported that enhancement of retronasal odors by
tastes is a more pronounced and reliable effect than enhancement of
tastes by odors. However, the degree of odor enhancement also
varied and appeared to be greater when the perceived intensity of
the odor was weak rather than strong. The present study was
therefore designed to investigate how the intensity of odors and
tastes affects the degree of retronasal odor enhancement. In the first
experiment Ss sampled aqueous solutions of two test odors (citral,
furaneol) at three concentrations with different levels of sucrose
(0, 0.18, 0.32, 0.56M) and rated the perceived intensities of
sweetness, sourness, saltiness, bitterness and “other” on the gLMS.
The addition of sucrose significantly enhanced (
p
<.05) the
perceived intensity of both odors (i.e., “other” ratings) to an extent
that was inversely related to their perceived intensities alone.
Interestingly, increasing sucrose concentration beyond 0.18M did
not necessarily produce further increases in odor enhancement.
To assess the reliability of the odor intensity relationship, a follow-
up study was conducted in which Ss inhaled three concentrations of
citral in vapor phase via the mouth while tasting a fixed
concentration of sucrose (0.32M). Consistent with the prior results,
the presence of sucrose in the mouth significantly enhanced citrus
odor ratings compared to when the citral odor was inhaled alone
(
p
<.001). Again, the degree of odor enhancement, however, became
smaller and insignificant as the perceived intensity of citral by itself
became stronger. These findings confirm that sucrose can enhance
weak, congruent retronasal odors in a manner that may serve to
strengthen the salience and thus the flavor identity of nutritive
foods. Acknowledgements: Supported by OSU start-up funds and
R01 DC005002
110 | AChemS Abstracts 2012
Abstracts are printed as submitted by the author(s)
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