Abstracts - Association for Chemoreception Sciences

with the latency of quinine-induced gape bouts. Our results
suggest that forebrain activity may influence certain aspects
of TR, such as the initiation of palatability-related orofacial
movements. Acknowledgements: DC007703
#P81 POSTER SESSION II:
OLFACTION DEVELOPMENT; TASTE CNS;
NEUROIMAGING; OLFACTION CNS
Neural dynamics in response to binary taste mixtures
Joost X Maier, Donald B Katz
Brandeis University Waltham, MA, USA
In natural environments, taste signals an animal encounters
typically consist of complex mixtures of tastants. Although a
great deal is known about how the taste system processes single
tastes presented in isolation, not much is know about how brain
integrates different taste signals presented simultaneously. Here
we probed single neurons in primary gustatory cortex (GC)
for responsiveness to binary taste mixtures. Stimuli consisted
of sucrose and citric acid and sucrose and sodium chloride
mixed in different ratios (100%/0%, 90%/10%, 70%/30%,
50%/50%, etc.). We tested for three different hypothetical
response patterns: 1) Responses varying as a function of sucrose
concentration (the monotonic pattern); 2) Responses increasing
or decreasing as a function of degree of mixture of the stimulus
(the mixture pattern); and 3) Responses that change abruptly
from being similar to one pure taste to being similar the other
(the categorical pattern). Our results demonstrate the presence
of both monotonic and mixture patterns within responses
of GC neurons. Specifically, further analysis (that included
the presentation of 50 mM sucrose and citric acid) made it
clear that mixture suppression reliably precedes a palatabilityrelated
pattern, and that the same phenomenon characterizes
responses to sucrose/NaCl mixtures. The temporal dynamics
of the emergence of the palatability-related pattern parallel the
temporal dynamics of the emergence of preference behavior for
the same mixtures, as measured by a brief access test. We saw no
evidence of categorical coding.
#P82 POSTER SESSION II:
OLFACTION DEVELOPMENT; TASTE CNS;
NEUROIMAGING; OLFACTION CNS
Conditioned Taste Aversion Does Not Require Cortical
mRNA Synthesis
Abigail A Russo 1 , Yasmin U Marrero 2 , Donald B Katz 1,2,3
1
Brandeis University Department of Psychology Waltham, MA, USA,
2
Brandeis University Program of Neuroscience Waltham, MA, USA,
3
Volen Center for Complex Systems, Brandeis University Waltham,
MA, USA
Although it has been well established that the gustatory cortex
(GC) plays a significant role in the consolidation of taste
memory, the precise physiological mechanisms by which this
takes place are not fully understood. Notably, taste memory
acquisition is traditionally viewed as dependent on cortical
protein synthesis (Dudai et al. 2004), but it is unclear whether
the learning process requires cortical mRNA transcription.
Here, we investigated this possibility using actinomycin D
(Act-D), an mRNA synthesis inhibitor that has been shown
to impair contextual fear conditioning when infused into the
amygdala (Parsons et al 2006). Act-D was microinfused via
cannulae implanted into the GC (1.4 mm anterior to Bregma,
5.0 mm lateral, 4.5 mm ventral) of awake rats. Immediately after
infusion, a conditioned taste aversion protocol was performed
during which the rats were exposed to a taste paired with
malaise. Our results indicated that rats form taste aversions even
when mRNA synthesis in GC is blocked. These results suggest
that memory consolidation is in part independent of mRNA
synthesis in the gustatory cortex. It is likely that subcortical
production of mRNA, presumably in the amygdala, is sufficient
to support cortical protein synthesis and establish taste memory.
Acknowledgements: R01 DC-006666/DC/NIDCD NIH HHS/
United States
#P83 POSTER SESSION II:
OLFACTION DEVELOPMENT; TASTE CNS;
NEUROIMAGING; OLFACTION CNS
Nutritive value, not taste, is necessary for flavor
preferences in mice
Jennifer M Stratford
Rocky Mountain Taste & Smell Center, Department of Cell and
Developmental Biology, Neuroscience Program, University
Colorado School of Medicine Aurora, CO, USA
The preference for food is dependent primarily upon the
interplay between oral and post-oral factors. The relative
contribution of these two systems to food intake is not fully
explored. Mice that lack the ability to taste, by genetic deletion
of the P2X2/P2X3 purinergic receptor subunits (P2X-KO),
can form a preference for monosodium glutamate (MSG) using
only post-ingestive cues. The neural mechanisms that underlie
this ability remain unknown but likely involve viscerosensory
detection of the nutritive qualities of MSG. Thus, the current
study assessed if P2X-KO mice can form a preference for the
calorie-free sweetener, SC45647 (SC), which, like MSG, is
appetitive to WT animals. WT and P2X-KO mice were given
training sessions with a flavor alone (e.g. cherry) or with a
different flavor (e.g. grape) mixed with 0.05 mM SC. Then all
animals were given 2-bottle preference tests with both flavors
without SC. During training, WT animals drank more SC
than did P2X-KO mice, suggesting that WT, but not P2X-KO
mice, can taste SC. However, neither WT nor P2X-KO animals
preferred the flavor that was previously paired with SC in flavor
alone preference tests. SC-evoked brain activation was measured
by expression of the immediate early gene c-Fos (cFLI) in the
nuc. solitary tract (nTS)- the primary taste/viscerosensory
nucleus. As previously reported for MSG stimulation, SCinduced
cFLI in gustatory (rostral) nTS was less in P2X-KO
animals compared to WT controls. In viscerosensory (caudal)
POSTER PRESENTATIONS
Abstracts are printed as submitted by the author(s).
60