Abstracts - Association for Chemoreception Sciences

of GSP neurons and 97% of PA neurons. The T-type Ca 2+ current
density in PA neurons was significantly larger than in the CT or
GSP neurons. CT, GSP and PA neurons had nimodipine-sensitive
L-type, w-conotoxin GVIA-sensitive N-type, and w-agatoxin
IVA-sensitive P/Q-type Ca 2+ currents and there were significant
differences in the expression of L-, N- and P/Q-type Ca 2+
currents between the CT, GSP and PA neurons. These results
indicate that subpopulations of GG neurons have distinct
biophysical properties of Ca 2+ currents, which possibly relate to
the types of receptors innervated by these neurons. Supported by
NIDCD grant DC-000288 (RMB).
#P179 POSTER SESSION IV: CHEMOSENSORY
TRANSDUCTION AND SIGNALING
Temperature Alters Summated Epithelial Potentials of
Tongue and Single-Cell Responses of Geniculate
Ganglion Neurons To Chemical Stimulation in Rats
Alexandre A. Nikonov, Robert J. Contreras
Department of Psychology & Program in Neuroscience, Florida
State University Tallahassee, FL, USA
Temperature is important for chemical sensitivity of taste
receptors and responsiveness of peripheral gustatory neurons.
In anesthetized male rats, we recorded stimulus-evoked lingual
potentials (electrogustogram; EGG) simultaneously with singlecell
2.5-s neural responses from 8 narrowly tuned (4 NaCl-best;
3 MSG-best; 1 sucrose-best) and 5 broadly tuned (5 citric acidbest)
neurons. We recorded EGG and single-cell responses to 100
mM NaCl, 100 mM MSG, 500 mM sucrose, 10 mM citric acid, 20
mM quinine HCl, and 100 mM KCl at least 3 times each between
23° - 41°C in both ascending and descending temperature steps of
3°C. Artificial saliva (15mM NaCl, 22mM KCl, 3mM CaCl 2 ,
0.6mM MgCl 2 ) served as the rinse solution and solvent for all taste
stimuli. Our preliminary findings show that temperature
influenced the average EGG response amplitude the most for
NaCl and KCl and the least to citric acid. The EGG response
amplitude to NaCl and KCl was optimal to 3 highest
temperatures (35, 38, 41°C) and declined progressively with
decreasing temperature to no response at 23°C. Temperature also
influenced breadth of tuning of neuron types. For example in
narrowly-tuned cells, NaCl-best neurons responded selectively to
NaCl across all temperatures between 41 - 28°C, but also
responded to KCl at 25 and 23°C. MSG-best neurons responded
selectively to MSG between 28-35°C, but also responded to
sucrose at 38 and 41°C. In contrast, broadly-tuned citric acid
neurons responded to all chemical stimuli at 35°C, but selectively
to citric acid at 23 and 25°C. Thus at lower and higher
temperature extremes, narrowly-tuned neurons became more
broadly responsive, while broadly-tuned neurons became more
narrowly responsive. Acknowledgements: Supported by NIH
grant R01 DC004785.
#P180 POSTER SESSION IV: CHEMOSENSORY
TRANSDUCTION AND SIGNALING
Primate Sweet taste is caused by impulses in a dedicated group
of taste fibers
Tiffany Cragin, Göran Hellekant
1
Department of Physiology and Pharmacology, Medical School,
University of Minnesota- Duluth, MN, USA, 2 Department of
Physiology and Pharmacology, Medical School, University of
Minnesota- Duluth, MN, USA
The division between a sweet and bitter taste quality is evident
already in the newborn. The discovery of a unique set of taste
receptors for the sweet and bitter taste quality provides an answer
to how sweet and bitter taste is created, but the question how this
information is coded in taste nerves remains an enigma. For many
years we have studied taste fibers in primates and found that their
single taste fibers cluster according to human taste qualities.
Comparisons of effects of the sweet taste modifiers gymnemic
acid and miraculin on behavior and taste fiber activity
demonstrate that liking of sweet correlates only with changes of
activity in fibers clustered as S (sweet best) fibers. Here we test the
validity of this theory with lactisole. It suppresses the human
sweet taste. We found that the intake of sweeteners by Macaca
fascicularis diminished significantly after 1.25 mM lactisole had
been added. The fact that the animals did not discriminate
between lactisole alone and water suggests that lactisole per se did
not influence preference. Recordings of 40 single taste fiber
showed that lactisole suppressed the response to sweeteners in
fibers responding best to sweet, the S-cluster, but had no effect on
the responses in fibers that responded to sour, bitter and salt, the
H, Q- and N-clusters. Lactisole had been reported to block the
T1R3 monomer of the sweet taste receptor T1R2/R3.
Consequently, these results suggest, not only that the perception
of the sweet taste quality is linked to activity in fibers of the S-
cluster, but also that the fibers affected conveyed taste from
T1R2/R3 receptors, while the source of the impulses in non-S
fibers are other kinds of receptors. Acknowledgements:
R01DC06016,
#P181 POSTER SESSION IV: CHEMOSENSORY
TRANSDUCTION AND SIGNALING
Taste-location generalization as a novel tool to study rodent
taste and flavor perception
Justus V. Verhagen 1,2 , John Buckley 1 , Michael Fritz 1 , Ron
Goodman 1 , Tom D’Alessandro 1 , Shree H. Gautam 1,2
1
The John B. Pierce Laboratory New Haven, CT, USA,
2
Yale University New Haven, CT, USA
In order to understand the perception of taste in rodents we can
use the established paradigms of conditioned taste aversion (CTA)
-generalization or the Morrison task. Our research into the neural
bases of taste-odor integration, has lead us to develop a new
technique to directly evaluate the on-line expression of taste
perception and taste-acquisition of odors by rats. This system has
been optimized to be compatible with extracellular recordings. It
is similar to the paradigm established by Youngentob, et al. (Phys
& Behav, p1053-1059, 1990) for odorants. Water-restricted rats are
taught to lick a central gustometer manifold presenting one of five
stimuli (water and four prototypical tastants), and subsequently
move to and lick water from one of five surrounding spouts. Only
licking the correctly mapped spout results in presentation of
water. Stimuli and responses are measured throughout the
P O S T E R S
Abstracts are printed as submitted by the author(s)
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