Abstracts - Association for Chemoreception Sciences

P O S T E R S
taste cells reveals several possessing a robust response to MSG,
including a synergistic response to MSG + IMP, which is the
hallmark of the umami taste response. In the c-Fos studies, we
show that the umami taste stimuli produced significant activation
of taste neurons in the PBN, including a subset of cells in the
dorsal lateral subnucleus (dls) of the PBN that project directly to
the LH. This pattern of labeling was comparable to that evoked
by sucrose, indicating that either sweet or umami stimuli produce
activation of a putative “appetitive” taste projection from the
PBN to the LH. Acknowledgements: Ajinomoto Research
Program (3ARP) NIH DC000353
#P288 POSTER SESSION VI:
PERIPHERAL AND CENTRAL TASTE;
PERIPHERAL OLFACTION
Quantification of c-Fos in the PBN reveals that visceral
response does not play a role in strain differences observed
in conditioned taste aversion between C57BL/6J and
DBA/2J mice
April R. Glatt, Kenichi Tokita, John D. Boughter, Jr.
University of Tennessee Health Science Center Memphis, TN,
USA
Objective: Previous behavior work has suggested differences
between C57Bl/6J (B6) and DBA/2J (D2) mice in the acquisition
and extinction of a conditioned taste aversion (CTA). This study
was conducted to investigate whether these results may be due to
the strength of the visceral response (malaise) resulting from the
unconditioned stimulus. Methods: B6 and D2 male mice received
intraperitoneal (i.p) injections of either a 20 ml/kg or 40 ml/kg
dose of 0.15 M LiCl. Two hours following injection, mice were
perfused and sections stained for the immediate early gene c-Fos.
We analyzed c-Fos expression in the parabrachial nucleus (PBN),
as it is suggested to be a site of convergence of visceral and
gustatory information, and plays a key role in CTA formation.
Strong c-Fos expression was found in the external lateral
subnucleus (ELS), which is known to receive primarily visceral
information. Results: First, we determined that c-Fos activation is
correlated to the degree of malaise induced by LiCl, as there were
significantly more FLI-positive neurons following the 40 ml/kg
dose compared to 20 ml/kg for both strains (B6, p ≤ .002; D2,
p ≤ .0001). Next we compared B6 and D2 mice at each dose, and
found no strain differences in number of FLI-positive neurons
following injections (20 ml/kg, p ≤ .48; 40 ml/kg, p ≤ .75).
Conclusions: We conclude that these results suggest that strain
differences observed in the acquisition or extinction of a CTA are
not likely due to varying degrees of malaise experienced, but
rather a result of CNS changes in gustatory or learning response.
Acknowledgements: DC000353
#P289 POSTER SESSION VI:
PERIPHERAL AND CENTRAL TASTE;
PERIPHERAL OLFACTION
An Analysis of Spike Timing in Parabrachial
Gustatory Neurons
Laura C. Geran, Susan P. Travers
The Ohio State University Columbus, OH, USA
Recent evidence suggests that in addition to spike rate, spike
timing may also help to distinguish among taste quality signals in
the brainstem and cortex. For instance, Di Lorenzo and colleagues
(2003, 2008) reported that 1/3 to 1/2 of neurons in the nucleus of
the solitary tract change best stimulus category over repeated
trials. Interestingly, such cells are more likely to show evidence of
temporal coding in a metric space analysis and to be broadlytuned.
We recently observed a population of narrowly-tuned,
bitter-best neurons in the parabrachial nucleus (PBN) that
responded in bursts of spikes, suggesting that other neuron types
might also exhibit temporal coding. To determine whether this
was the case, we recorded from taste-responsive PBN cells over
multiple trials, applied metric space analysis, and examined
bursting patterns. These parameters were compared across cells
for best stimulus, breadth of tuning and receptive field. Neurons
were tested at least 10 times on each of 5 different stimuli (0.3M
sucrose, 0.1M NaCl, 0.03M citric acid, 0.03M quinine and 10 mM
cycloheximide). Preliminary analysis revealed that best stimulus
category changed only rarely over repeated trials, and in contrast
to solitary nucleus neurons, the few cells that did switch best
stimulus were not more likely to show evidence of spike timing.
However, narrowly-tuned bitter-best neurons had a greater
percentage of spikes occurring within bursts (p