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activated by suprathreshold LOT stimulation such that the imaged
calcium transients were due to action potentials in individual
neurons. In each slice, a significantly greater number of cortical
neurons responded to 2 Hz (10 ± 5) versus 8 Hz (5 ± 3, p<0.01)
stimulation. Typically, neurons that spiked during 8 Hz stimulation
also responded to 2 Hz stimulation (n=60), while additional
neurons responded solely to 2 Hz stimulation (n=70). Following
population imaging, targeted patch clamp recordings were made
from neurons that responded to both stimuli (2 Hz and 8 Hz) or
solely to 2 Hz stimulation. Cells that spiked in response to both
stimuli received facilitating synaptic input during subthreshold
LOT stimulation (n=9). Cells that responded solely to 2 Hz stimuli
received depressing synaptic input (n=10). These results suggest
that short-term plasticity at LOT synapses contributes to differential
cortical population responses to stimuli delivered at passive (2 Hz)
versus active (8 Hz) respiratory frequencies. Acknowledgements:
NIDCD: R03DC011375 to AMMO, R01DC0005798 and
R01DC011184 to NNU
#P234
POSTER SESSION VI:
OLFACTION CNS; TASTE PERIPHERY &
CNS; MULTIMODAL RECEPTION
TRP channels underlie temperature-mediated changes in
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
In our prior studies we showed that stimulus temperature
influenced the response patterns of geniculate ganglion (GG)
neurons to the basic taste stimuli. To determine the contribution
of the transient receptor potential (TRP) channel to coding, we
recorded stimulus-evoked lingual potentials (electrogustogram;
EGG) simultaneously with single-cell 2.5-s neural responses from
12 narrowly tuned (5 NaCl-best; 5 MSG-best; 2 sucrose-best) and
15 broadly tuned (10 citric acid-best, 5 NaCl generalist) GG
neurons. We adapted the tongue at two different stimulus
temperatures of 20° and 35° C and recorded EGG and GG neuron
responses to 100 mM NaCl, 100 mM MSG, 500 mM sucrose, 10
mM citric acid, 20 mM quinine HCl, and 100 mM KCl at two
different stimulus temperatures of 18°- 23° and 25°- 38° C with a
two-channel temperature control system. Additionally, we used
Ruthenium Red (20-50 µM) as a nonspecific antagonist of TRPV
channels. 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 results show that the addition of
Ruthenium Red (50 µM) to the rinse solution altered the responses
of broadly tuned GG cells (13 from 15 cells) adapted to 35°C, but
did not alter their responses when adapted to 20°C. The effect of
Ruthenium Red was reversible as normal responses were restored
after 5-8 min of control rinse. The Ruthenium Red did not change
the responses of narrowly tuned cells (11 from 12). Only TRPV3
and TRPV4 from TRPV subfamily are active at 27°- 35° C. The
present results suggest the participation of vanilloid channels in
coding taste quality information by the peripheral gustatory system.
Acknowledgements: NIH grant R01 DC004785
#P235
POSTER SESSION VI:
OLFACTION CNS; TASTE PERIPHERY &
CNS; MULTIMODAL RECEPTION
Delayed effects of lipopolysaccharide ingestion on peripheral
taste function
Xiaobin Zhu
1,2
, Lynnette P McCluskey
1
1
Georgia Health Science University Augusta, GA, USA,
2
Zhongnan Hospital of Wuhan University Wuhan, China
Lipopolysaccharide (LPS) is an endotoxin derived from Gram-
negative bacteria, which are frequent contaminants of food and
water. We tested whether LPS modulates taste input to the CNS by
recording chorda tympani nerve (CT) responses to taste stimuli in
C57BL/6 mice. First, we recorded CT responses before and after 10
min lingual application of LPS (10ug/ml). LPS (5ug/ml) was also
present in the diluent of tastants applied during the second series.
Acute treatment with LPS did not alter the magnitude of CT
responses. Next, we provided water-deprived mice with 12 hr
access to LPS (10ug/ml) diluted in 5% sucrose, or sucrose alone.
CT recordings were then performed at day 1, 7, or 14 days after
LPS ingestion. At day 1 post-ingestion, responses to salt, bitter,
umami, and sour stimuli were similar between groups. However,
at day 7, neural responses to 0.50 M and 1.0 M sucrose were
significantly reduced in mice that drank LPS compared to controls.
Mice that drank LPS mixed in 0.15 M NaCl also exhibited reduced
CT responses to sucrose, indicating that the effect is dependent on
LPS rather than the vehicle. CT responses returned to normal by
day 14 after LPS ingestion. A transient drop in sweet signals to the
CNS, perhaps via downregulation of T1R2 and/or T1R3 in taste
cells, may reduce the appeal of endotoxin-tainted nourishment.
Acknowledgements: NIDCD DC005811
#P236
POSTER SESSION VI:
OLFACTION CNS; TASTE PERIPHERY &
CNS; MULTIMODAL RECEPTION
Capsaicin given orally in moderate doses does not produce
edema in rat tongue tissue
Jacquelyn M. Davis, Suzanne I. Sollars
University of Nebraska at Omaha/Psychology Omaha, NE, USA
Capsaicin, the chemical irritant that gives peppers their
characteristic spicy heat, is commonly consumed around the world
as a daily component to many animal and human diets. Capsaicin is
known to cause damage to TRPV1 receptors and thus provides an
ideal natural approach to assessing damage and recovery in the
taste system (Nagy, Santha, Jancso & Urban, 2004). Earlier work
from our laboratory examined the effects of 1 ppm capsaicin on
taste bud volumes (Samson & Sollars, 2010). This work produced
interesting though variable results, thus we sought to determine the
potential source of the variance. Evans Blue dye was used to
examine whether a slightly higher level of capsaicin (5 ppm) causes
acute localized edema. Previous research identified capsaicin-
related swelling in rats at much higher dosages (100 ppm) and was
proposed as a potential cause for the taste differences seen with
frequent users of capsaicin (Simons, Boucher & Carstens, 2003).
Thus identification of whether swelling occurs in animals treated
with a much lower dose provides clarification as to whether the
variance in our previous study may have been produced by the dose
of capsaicin used and allows us to consider using a higher dose of
capsaicin to examine effects on taste buds. Edema was tested by
injection of Evans Blue followed by capsaicin application to the
tongue and perfusion. Capsaicin at 5 ppm (in ethanol) did not cause
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