Basic HTML Version
26 | AChemS Abstracts 2012
Abstracts are printed as submitted by the author(s)
#52
SYMPOSIUM: THE ROLE OF RESPIRATION IN
OLFACTORY & FLAVOR PROCESSING
Sniff-locking of mitral and tufted cells: Two distinct temporal
channels of olfactory bulb output
Andreas T. Schaefer, Manuel Berning, Mihaly Kollo,
Anja Schmaltz, Izumi Fukunaga
MPI f. med. research / Behavioural Neurophysiology
Heidelberg, Germany
Rhythmic neural activity is a hallmark of brain function, used
ubiquitously to structure neural information. In mammalian
olfaction, repetitive sniffing sets the principle rhythm but little is
known about its role in sensory coding. Here, we show that mitral
and tufted cells, the two main classes of olfactory bulb projection
neurons, tightly lock to this rhythm, but to opposing phases of the
sniff cycle. This phase shift is established by local inhibition that
selectively delays mitral cell activity. Furthermore, while tufted cell
phase is unperturbed in response to purely excitatory odorants,
mitral cell phase is advanced in a graded, stimulus-dependent
manner. Thus, phase separation by inhibition forms the basis for
two distinct channels of olfactory processing. Acknowledgements:
Max-Planck Society, DFG, Humboldt foundation
#53
SYMPOSIUM: THE ROLE OF RESPIRATION IN
OLFACTORY & FLAVOR PROCESSING
Phase coding in Olfaction
Dmitry Rinberg
1
, Roman Shusterman
1
, Matt Smear
1
,
Thomas Bozza
2
1
Janelia Farm Research Campus, HHMI Ashburn, VA, USA,
2
Northwestern University/Neurobiology Department
Evanston, IL, USA
In mammals, the temporal dynamics of olfactory stimuli are
largely determined by breathing, which gates access of odorants
to olfactory receptor neurons. To establish the relationship
between the sniffing/breathing rhythm and neuronal coding of
odor information in the olfactory bulb we recorded activity of
mitral/tufted cells in awake headfixed mice. We found that the
firing rate odor responses of mitral/tufted cells are locked to the
phase of the sniffing cycle with high temporal precision about
10 ms. Thus temporal sequence of neuronal events scales with the
duration of the sniffing cycle. We proposed the model of how the
cortex may solve the odor identification problem independently
of the pace of inhalation based on the synchrony between cell
assemblies. To proof that an animal can perceive the sniff phase
we performed behavioral optogenetic experiments stimulating
olfactory receptor neurons, which express ChannelRhodopsin with
short light pulses at different phases of sniffing cycle. Mice can
report the shiff phase of optogentically driven activation of
olfactory sensory neurons. Furthermore, mice can discriminate
between light-evoked inputs that are shifted in the sniff cycle as
little as 10 ms, which is similar to the precision of the olfactory
bulb odor responses. Our work suggests that timing of activity
relative to the sampling behavior is a potent cue that may enable
accurate olfactory percepts to form quickly. Acknowledgements:
HHMI funding
#54.5
CLINICAL LUNCHEON
Bitter taste, a major determinant for food preferences
Wolfgang Meyerhof, German Institute of Human Nutrition
Potsdam-Rehbruecke, Department of Molecular Genetics,
Arthur-Scheunert-Allee
The sense of taste enables mammals to decide within seconds if a
mouthful can be swallowed because it is safe and of nutritional
value or is to be rejected because it contains potentially harmful
substances. Errors could have serious health problems ranging from
malnutrition to acute or chronic intoxication. Each basic taste
fulfills a specific role in the food evaluation process. Bitter taste
detects potentially harmful substances and is associated with
neuronal networks that elicit rejection, thereby preventing food
poisoning. It involves the recognition of countless molecules with
different chemical structures. Depending on dose, these molecules
can be toxic or healthy. Accordingly, consumers strongly prefer
some bitter tasting foods and beverages whereas they avoid others
indicating that bitter chemicals exert strong effects on food choice,
and eventually diet and health.
My group aims at a fundamental understanding of the importance
of bitter taste for food preference and rejection. To this end my
presentation summarizes our recent results of research into bitter
taste. Starting from a description of bitter chemicals, I will examine
the interaction of bitter compounds with their receptors, describe
the expression profile of bitter taste receptors in oral sensor cells,
and analyze how these sensor cells are coupled to the 1st order
central gustatory neurons in the brain stem. Finally, I will present
data on how oral bitter stimulation initiates behavioral responses
The results of above experiments will be described and their
implication for bitter taste driven appreciation or rejection of
food discussed.
#55
SYMPOSIUM: MODULATION OF EARLY
OLFACTORY PROCESSING BY INTERNAL
PHYSIOLOGICAL STATES
Neuromodulatory Effects in the Olfactory epithelium Vary
with Odorant and Physiological State
Heather L Eisthen
Michigan State University, Dept of Zoology East Lansing, MI, USA
The terminal nerve extends between the nasal cavity and basal
forebrain, and its fibers contain a number of potentially
neuromodulatory compounds. Working with aquatic salamanders,
axolotls (Ambystoma mexicanum), we have been examining
modulatory effects on the olfactory epithelium of two terminal
nerve peptides, gonadotropin releasing hormone (GnRH) and
neuropeptide Y (NPY). Although GnRH is often associated with
reproduction and NPY with feeding, our studies indicate that both
peptides modulate activity in the olfactory epithelium in complex
ways: their effects depend on the animal’s sex, nutritional state,
and reproductive state, as well as the behavioral significance of
the odorant. For example, electro-olfactogram (EOG) responses
evoked by whole-body odorants from females are suppressed in the
presence of GnRH in males with a larger gonadosomatic index
(GSI) but are unchanged in males with a smaller GSI. Among
females exposed to GnRH, EOG responses evoked by females
odorants increase in low-GSI, food-deprived animals, remain
constant in low-GSI, well-fed animals, and decrease in high-GSI
animals. In contrast, we find that isoamyl acetate, a behaviorally
meaningless odorant for axolotls, evokes fairly constant responses
O R A L A B S T R A C T S