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for operant conditioning. WT mice challenged with higher fat diets
became hyperglycemic whereas fasting glucose levels and body
weight remained low in KO mice, only elevating to CF levels of
WT mice when placed on the HF regime. Regardless of body
weight, mice maintained on higher fat diets required twice as many
learning trials to achieve 80% accuracy determined by the animal
licking 6 of 10 short time bins following the presentation of an
odorant to receive a water reward (Stage 3). Once the task was
learned, HF challenged WT mice had a reduced accuracy in
go-no-go trials to recognize the trained odorant, difficulty in
discriminating at asymptotic levels of performance between two
structurally dissimilar odors, and only one could relearn a task
following switch of the conditioned odorant (S+) with the
unconditioned odorant (S-). HF challenged, but obesity resistant,
KO mice had no difficulties recognizing the trained odorant,
demonstrated increased discrimination between two odorants over
that of CF KO mice, but showed a slower time to initially relearn a
task (i.e. S+/S- switch) compared to WT mice. These data suggest
that high-fat diet contributes to impaired olfactory-based learning
whereas related changes in body weight additionally affect the
accuracy of olfactory discrimination. Acknowledgements: This
work was supported by NIH R01003387-SUMM by the NIDCD, a
Bess Ward Scholarship from FSU, a Johnson Award from TriBeta
National Biology Society, and an equipment grant from the FSU
Program in Neuroscience.
#P135
POSTER SESSION IV:
CHEMICAL SIGNALING & BEHAVIOR;
PSYCHOPHYSICS; CHEMOSENSATION & DISEASE;
OLFACTION PERIPHERY; TASTE PERIPHERY
Olfactory sensitivity and odor structure-activity relationships
for aliphatic carboxylic acids in CD-1 mice
Selcuk Can Guven, Matthias Laska
Linkoping University Linkoping, Sweden
Using a conditioning paradigm, the olfactory sensitivity of CD-1
mice for a homologous series of aliphatic n-carboxylic acids
(ethanoic acid to n-octanoic acid) and several of their isomeric
forms was investigated. With all 14 odorants, the animals
significantly discriminated concentrations ≤0.03 ppm (parts per
million) from the solvent, and with four odorants the best-scoring
animals even detected concentrations as low as 3 ppt (parts per
trillion). Analysis of odor structure-activity relationships showed
that the correlation between olfactory detection thresholds of the
mice for the unbranched carboxylic acids and carbon chain length
can best be described as a U-shaped function with the lowest
threshold values at n-butanoic acid. A significant positive
correlation between olfactory detection thresholds and carbon chain
length of the carboxylic acids with their branching next to the
functional carboxyl group was found. In contrast, no such
correlation was found for carboxylic acids with their branching at
the distal end of the carbon chain relative to the functional carboxyl
group. Finally, a significant correlation was found between
olfactory detection thresholds and the position of the branching of
the carboxylic acids. Across-species comparisons suggest that mice
are more sensitive for short-chained (C
2
to C
4
) aliphatic
n-carboxylic acids than other mammalian species, but not
for longer-chained ones (C
5
to C
8
). Further comparisons suggest
that odor structure-activity relationships are both substance class-
and species-specific.
#P136
POSTER SESSION IV:
CHEMICAL SIGNALING & BEHAVIOR;
PSYCHOPHYSICS; CHEMOSENSATION & DISEASE;
OLFACTION PERIPHERY; TASTE PERIPHERY
Changes in odor-guided learning mirror changes in cortical
dopamine function.
Chloe R. Lawyer, Anna K. Garske, Brittni M. Peterson, Kurt R. Illig
Department of Biology and Program in Neuroscience,
University of St. Thomas Saint Paul, MN, USA
The orbital frontal cortex (OFC) and piriform cortex are highly
interconnected structures that are thought to be involved in
encoding the predictive value of environmental stimuli. Each of
these cortical areas displays experience-dependent plasticity, which
may be modulated by mesocortical dopamine (DA). The
importance of DA in associative learning appears to change during
development; adolescent rats demonstrate a greater behavioral
sensitivity to drugs that act on DA receptors compared with
juvenile and adult rats, require more trials to extinguish cocaine
place-preference than adults, and exhibit higher susceptibility to
reinstatement in studies of cocaine-seeking behavior. Changes in
DA receptor expression throughout the lifespan may underlie these
age-dependent differences in learning the predictive value of
environmental cues. Previously, we described changes in DA
receptor expression during adolescence. Here, we confirm these
findings with quantitative PCR and immunocytochemical data, and
show that adolescent rats exhibit significantly slower learning on an
odor discrimination task compared with juvenile and adult rats.
This impairment was alleviated by administration of a low dose of
the DA receptor agonist SKF-32393. These results suggest that DA
plays a role in learning the predictive value of environmental
stimuli, and that developmental changes in DA receptors may
underlie age-related differences in odor-guided associative learning.
#P137
POSTER SESSION IV:
CHEMICAL SIGNALING & BEHAVIOR;
PSYCHOPHYSICS; CHEMOSENSATION & DISEASE;
OLFACTION PERIPHERY; TASTE PERIPHERY
Effects of Cholinergic Receptor Inhibition on Olfactory Fear
Learning and Generalization in Mice
Eloisa Pavesi, Allison Gooch, Elizabeth Lee, Max L. Fletcher
University of Tennessee Health Science Center/Anatomy and
Neurobiology Memphis, TN, USA
Fear conditioning has long been used as a powerful model for the
study of the neural mechanisms behind learning and memory.
Here we use this model to investigate the role of cholinergic
neurotransmission in olfactory learning. Under control conditions,
mice receiving pairings of an olfactory stimulus with aversive foot
shock display robust fear towards the trained odorant as measured
by stereotypical freezing behavior. We next applied systemic
injections of cholinergic antagonists prior to pairing an odorant
with aversive foot shock and measured freezing to the trained
odorant as well as similar odorants the following day. Injections of
the nonselective nicotinic antagonist mecamylamine before training
had no effect of subsequent freezing levels. However, pre-training
injections of the muscarinic antagonist scopolamine significantly
reduced freezing to the trained odor in a dose-dependent manner.
Additionally, scopolamine also reduced freezing to other similar
odorants compared to control mice. While there was an overall
reduction in freezing levels to all odorants in scopolamine treated
animals, the amount of generalization remained similar in both
control and scopolamine groups. Overall, these results suggest that
72 | AChemS Abstracts 2012
Abstracts are printed as submitted by the author(s)
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